So this is what happens when I think way too hard about the backstories of minor characters:

After all the hubbub with Mira and Ian really drives home just how much of his humanity Dipper had been losing without noticing, he decides at some point (maybe during Mira’s life, maybe shortly after) to make more of an effort to forge some more human connections.  Not put all of his “keep -connected-to -humanity” eggs in one basket, so to speak.  (A lesson he’ll need to reapply many times over the centuries, e.g. when Bentley rolls around.)  Of course he’s got Mira and Ian’s kids and their eventual families, but that also gets him nostalgic for the time when he was a regular fixture of Mabel’s descendants’ lives.

Of course, by this point they’re far too numerous and spread-out and of diverse opinions (and knowledge levels) regarding their family history for keeping up with all of them to be practical.  But as it happens, the now-sentient Wandering Shack is still owned (on paper at least) and cared for by one branch of the Pines family.  So when it drifts back to the Gravity Falls area and decides to stick around for a while (though in different spots from week to week – I like the idea that it likes to pull the “magic shop that wasn’t there yesterday” shtick just for kicks) Dipper takes the opportunity to reintroduce himself to his family.

The first of these new niblings is Vanessa Pines: Jerry’s mother and his predecessor as caretaker/public face of the Library.

Vanessa would be described by most people who know her – from one-time Library visitors to her own son – as a…character.  She’s ultimately a nice person, but is very zealously and overdramatically devoted to the family legacy and the integrity and safety of the Shack, and her presence can be very overwhelming.  She has a good deal of the Stanley genes in terms of showmanship and over-the-top theatrics and wild claims – but unlike Stan, she usually doesn’t drop the act once the customers leave.  “Large ham” is her default state, even more so as she gets older, and it becomes increasingly difficult for even those closest to her to tell how much is just an affected persona and how much is really just her.

Truthfully, she’s not really sure either.  But she has too much fun to care.

Vanessa’s line of the Pines family has largely remained with the Shack/Library over the years, and knows more about the family history than most.  There are still many large gaps in their records, though, and given that Alcor hasn’t visited in generations (and the well-publicized results of his more inhuman phases leaving them wary of using the old summoning circle arts & crafts gathering dust in the basement), they’ve had no personal experience with him to confirm any of the old family stories.

So Vanessa (the only one of her siblings and cousins who lives at the Library full-time) is very much thrown off guard when the Devourer of Souls randomly pops in one day, casually bypassing all the wards, with a goofy shark-toothed grin and a cheerful “Hi, family!”

She recovers quickly, however, and launches immediately and comfortably into her element: dramatically proclaiming herself the guardian of this ancient bastion of knowledge and trying to banish him five different ways and shrewdly deducing his sinister plot to beguile her and take the Library for his own but oh she sees through his silver-tongued lies and even if she falls the Shack itself has greater power than he knows and will ultimately defeat him and how foolish he was to come here etc. – all before he even finishes introducing himself.  Dipper, impressed by her audacity, waits patiently until she starts to wear herself out (a good fifteen minutes – she clearly got no small amount of Mabel’s energy), then explains his deal to her.

She listens, stony-faced, but Dipper can’t help but notice that her aura kind of dims in disappointment when he assures her that he just wants to get to know the family again, and tries to be calm and placating and non-demony.  He feels strangely like he’s let down a child who thought she’d just been offered an early birthday present.

So, not wanting to start off their relationship by making his nibling sad, he awkwardly pretends to offer her a very one-sided deal.  It’s laughably transparent and nowhere near his best effort, but it does the trick: Vanessa instantly perks back up and gleefully denounces him, proclaiming defiantly that he can come back as many times as he wants (she’s very clear with that wording) but she’ll never be fooled by his foul tricks.  Also that she’s making tuna casserole tomorrow for dinner so if he wants to have another futile go at this he might as well do it then, so she can refuse his evil offers over a good meal.

Dipper’s subsequent visits end up being the most fun Vanessa’s had in a long time.  For his part, Dipper quickly becomes very fond of her, and enjoys humoring her with demonic threats and monologues whenever he visits.  (Anyone who saw their interactions would find it hard to believe that Vanessa doesn’t sincerely view him as a recurring villain in her life’s story, but Dipper knows they’re buds.  …Well, he’s 99.9% sure.)  Over time he gets introduced to the rest of her close relatives, including young Jerry (who was away living with his father during the above events), with whom he gets the joy of once again being a “Grunkle” to a Pines child.

While Vanessa never married, she did have many short-term flings over the years, one of which resulted in her only child.  Jerry was quite unexpected – Vanessa was middle-aged by then (early fifties) and fairly certain she was past the point of this being a potential thing.  Though she absolutely despised the experience of being pregnant, and gave her poor obstetrician lifelong nightmares from her behavior during the birth (true to form, her obscenity-laden threats of physical/magical retribution against all involved parties were delivered in both gruesome detail and deadly seriousness), once Jerry finally arrived she proved to be a very dedicated single mom.  While still approaching the task with the same dramatic flair with which she colors every other aspect of her life, of course.

She’d never planned on having children, trusting that when it was time the Shack would find an ideal successor if it wanted one, or it would just decide to finally go its own way without human caretakers.  But little Jerry loved the Shack and learning all its secrets, and the Shack seemed to love him back, so there was really no question in Vanessa’s mind that he would be the one to take over from her when he was old enough.

Jerry’s father shares custody with Vanessa, though he’s very much a “free spirit”, hippie-type personality who hates settling down in one place for too long and travels the world on his whims.  As a kid Jerry spent about a third of the year travelling with his dad and the other two-thirds living with Vanessa.  Surprisingly, between growing up in a sequence of hostels, rented cabins, and trailers with his dad and a sentient, wandering library with his mom, Jerry turns out largely grounded in temperament, in marked contrast to both his parents.

Indeed, even as a young child, Jerry often feels that he’s the parent to two wild, exasperating kids.  He does love both his parents, but is honestly glad that they’re not together.  Having to deal with them one at a time is taxing enough; he can only shiver at the thought of what they’d be like if they joined forces.

Jerry is in his late teens when Dipper casually mentions one day that he’s purchased a house for reasons, no biggie just a thing he wanted to do, and could Jerry maybe come take a look just to make sure it looks normal and unsuspicious from a human perspective?  And, just a random, completely-irrelevant-to-anything-that-I’m-doing question, does he think it would be a suitable habitation for, oh, let’s say, some hypothetical seven, eight-year-old human child?  (Then he gets grumbly when Jerry firmly vetoes all of his totally-practical add-ons, like the closets leading to infinite space-time loops and the chomping shark teeth on the window rims.  “Why would humans not have them, they’re a perfect deterrent against home invaders!”)

By the time Maddie is born, Vanessa is retired and off travelling on her own.  Jerry wouldn’t have minded her staying with him in the Shack, but she makes such an impassioned production of tearfully “passing on this indescribable, ancient burden” to Jerry and rejoicing in finally “casting off the invisible shackles that have burned unseen against my flesh from the very fundament of this life’s memory,” that he just sighs and indulges her with a smile.  She’s happy, and he has his actual kids to raise now, anyway.

—

((And here, just because I’ll probably rarely if ever use Vanessa in any meaningful capacity, have a brief example of a typical interaction between Dipper and the new niblings.))

Dipper: [blips in] ’Sup, Nessa?

*Vanessa springs to her feet like a startled cat, gathers the scrolls she was studying in front of her like armor, and hisses, also like a startled cat.*

Vanessa: DEMON!  Vile creature of hellspawn!  Away with you!  AWAY!!!

*She holds a hand in front of her in a gesture that most folks of the day would assume in this context to be some sort of arcane symbol to ward against evil.  Dipper recognizes it as a twenty-first century “peace” sign.*

Dipper: [patronizing demonic smirk mixed with genuine fondness] Oh, p̷l̢eáse̡, Vanessa, you know that one won’t work on me.  I’m much too powerful for that.

Vanessa: Wretched fiend!  Your perfidious words have no power in this hallowed place!  Woe, woe betide you should you remain, though you think to soil this ancient temple of knowledge with your profane presence!  It shall spell your ultimate undoing!

Dipper: Yuh-huh.  Woe.  I remember.  Is Jerry home?  I’d like to talk to both of you.

*Jerry enters the room, attracted by the noise and resigned to dealing with whatever’s set his mother off this time.*

Jerry: [bored] Ho-kay, what’s come alive and is eating the Library today, Mom? [notices Dipper, smiles.] Oh, hey, Grunkle Dipper.

Vanessa: Foolish boy!  You would court the attention of this most devious of villainous beasts, one whose corrupting touch stains naught less than the very fabric of space and time through which he passes, so easily?!  Have I taught you nothing?!

*Dipper floats over to Jerry and puts a companionable arm around his shoulders, smirking.  Jerry just rolls his eyes at them both.*

Dipper: You’re slipping up, old woman.  My influence on your blood grows stronger by the day.  Sooner or later, the kid will succumb to my wiles, and then the Library will be m҉̹̘̖̻̞̤ͅį͎̝͍͎̻͎n̢͎̯e͖̘͘.  [hesitates] …Right?  That’s, that’s what I’m going for, isn’t it?

*Vanessa briefly drops her righteous outrage to give a quick confirming nod.*

*A young tourist couple walks up the steps of the Library.  With instincts finely attuned to anything approaching her home, Vanessa instantly diverts her attention to them, using an upgraded version of Stan’s old smoke bombs that allow actual short-range teleportation to pop up right in their faces the second they open the door.*

Vanessa: BEHOLD!  You have crossed the threshold of this place of ancient power and history!  You are now bound forevermore to the fate that has brought you hence!  Should you break your unspoken vow, your very spirit shall know no rest, but shall linger on in these hallowed halls, lost and bereft, alone save for those likewise indentured souls stretching back through the cent-

Jerry: [sigh] Mo-o-om, you’re scaring the paying customers again, we need those to earn a living, remember…?