Of course he was nervous around each of their new companions when they first joined them, though he took to Keyleth surprisingly quickly. (And when Vex would've thought the opposite; her changing species must have seemed bizarre to him at first.) It wouldn't be until Tary joined them that he showed himself more used to new friends coming in. So it made sense when he was initially wary of Percy.
When the possibility of marrying Percy started feeling like more of a probability, Vex asked Trinket, on a lazy day where she could cast Speak with Animals multiple times without worry, what he thought about that. Trinket was generally happy with the idea; he knew Percy made her happy, and had become convinced he'd make a good mate, too. "I think he was a threat once, but now he just protects us, right?"
Vex regretted then that she couldn't really ask him what he meant by that; getting that sort of nuance was beyond the abilities the spell gave them. Although Trinket, since he had reached adulthood, had witnessed enough behavior from the people around him that he could usually tell the basics of what was going on. And of course, not only had he been present for the conversations they'd had with Percy when they'd been trying to free Whitestone, but he'd first seen the smoke, and then even delivered the final blow on the entity responsible when they'd first fought him.
So he might have easily just meant all that. But it was then that she also thought how how he'd constantly been sniffing at Percy and looking nervous around him during his first days with the group, and so also wondered if he'd marked Percy as a threat for much longer, for different reasons. Or maybe his having the sticks that made big scary noises had just freaked him out, and the behavior before he first fired them had been because he'd been the only newcomer to focus on.
In any case, Vex hadn't needed magic to understand Trinket's behavior when he was one of the few present when she married Percy. The way he ruffled against him and and growled softly spoke an obvious message she translated for him: Trinket would give Percy a fair chance to be a good mate, but would keep a sharp eye on him nonetheless. Of course, Percy declared himself quite glad to know Trinket was doing his part both keeping him in check, and protecting Vex.
Her thoughts about what Trinket could sense in Percy returned one more time: during her fourth pregnancy, where a constantly elevated body temperature served as an indication their fifth child might turn out to be a Tiefling. Trinket, who had already shown an ability to detect her pregnancies himself and maybe get more solicitous of her as a result, this time, on one still early day, went sniffing at her womb, then stared as her with an expression so flummoxed she very nearly laughed.
Except it wasn't entirely funny, as she then cast the spell and asked him, "You don't think I'm being threatened, do you? You've never had a problem with Zahra, not really."
"A cub's never a threat!" Trinket exclaimed. "And you don't smell like Zahra, you smell like Percy when he was dangerous. It's weird."
Most of that was reassuring, but Vex did feel the need to ask, "You won't go ask him for inflicting this particular baby on me, will you?"
Trinket seemed to have to think about that for a moment, but then said, "Not so long as he continues to be good to you and to all your cubs."
He got over the smell, after that. It was true he'd never had a problem with Tieflings, and when Gwen was born, she really was like her siblings had been to him. Vex wasn't sure if he really even understood how she was different, even if she'd cause her mother to smell different. He did seem to eye Percy a little more in the days following the birth, but if anything he was even more of an attentive husband and father than he had already been, and Trinket probably couldn't even recognize the guilt in his eyes. Bears didn't feel guilt, beyond maybe an occasional immediate and brief reaction to having gotten someone they cared about hurt.
Ultimately, by that time in his life, Trinket definitely had his own views about mates and the raising of cubs. They were ones, Vex knew, that weren't a normal bear's views, if a normal bear's attitudes towards the subject could even be called that. This became very clear when, not long after Gwen's birth, he unexpectedly found a mate of his own.
He really hadn't had much contact with other bears in general, and none for years, when a female bear wandered into the Parchwood and made it her home. Trinket actually found her by himself weeks before anyone in the Grey Hunt did, and they found it suitable to mate with each other soon after that. But then Trinket showed her Whitestone, and managed to communicate to her that he wanted them to raise their cubs together in the castle, which had confused her greatly.
"Boy bears don't do that," she explained to Vex, when they magically conversed for the first time. "I know some boy animals do that, but bears don't. My mom mated with my dad, then they went away from each other, and she raised me without him, and I can raise my cubs the same way."
It made Vex think for the first time that maybe what she'd done with Trinket, raising him so much in the world of people, especially when she and Vax had stopped living so much in the woods, had been a little bit of an extreme thing to do with a bear. Not a wrong thing, necessarily, if only because there hadn't been many options when she'd first taken him away, but still.
Eventually, the idea of having constant warmth and food available brought Trinket's new mate to the castle shortly before she gave birth. Both she and Trinket warned Vex, though, that she had no intention of being a fully domesticated bear. She even requested they not give her a name. "Animals have names when they belong to people," she said. "I won't belong to people." Vex duly instructed everyone to not name her; she could be referred to easily enough just as "Trinket's mate."
Percy had already agreed to take her in, and he even allocated the bears their own space within the castle, one that made it easy enough for them to also act as guard bears when they were there and awake. But Vex, to her own private amusement, sometimes thought his reaction to her was not unlike Trinket's friendly but ever watchful reaction to him had been.
"Well, of course I have concerns," Percy said to her. "Remember wild bears often view people as for eating, even if Trinket has no doubt made clear to her we aren't, and you even said she won't be tamed entirely. But if she has accepted we're not to be harmed, well, then, let Trinket have his mate here, right alongside yours."
She came and went as she pleased, sometimes disappearing off into the woods for days at a time. After Charlie was born, she usually took him with her, determined he would know how to live as a wild bear as well. Sometimes Trinket went with them, too, and Vex thought he looked a bit refreshed when they came back. Which kept her from minding; indeed, she couldn't help but admire her determination.
She also responded more to the advent of winter than Trinket did. Neither of them had to fully hibernate when living in Whitestone, but even as he showed all the signs of how much older than her-and most other bears-he was, she was the only who slowed down and was much less inclined to step outside the castle once it got cold enough. Which, ironically, meant that when little Vax'ildan and Charlie decided that was when they wanted to venture out on their own for the first time, it was her, sleepy and possibly also pregnant again, who stayed behind in the castle, and Vex and Trinket who walked them to the outskirts of town.
There Vex hugged her son, whispered him her various reminders all over, and told her she loved him, while the bears said farewell with soft sounds and headbutts. They stood together, listening, until their sons could no longer be heard even by Trinket's ears.
On the way, Trinket gave Vex the specific whine that had become his way of requesting she cast Speak with Animals. When she did, he said, "I think Allura was right, that I won't die until you do. I feel old, but I think I should feel older."
"Does it bother you?" Vex asked. "I don't want you to leave me ever, but if staying that long would be too much for you..."
"I don't want to leave you alone," said Trinket. "I know it'll be bad once they starting dying."
"Not all of them will," said Vex. "Some of our friends will live even longer than me. And also, I've been talking with Keyleth about Danny, and she says he might become like her, which would make him live a very long time as well. Or he might be become like me, and Charlie might live as long as him, then."
"That would be nice," said Trinket.
The spell had worn off by the time they reached the castle, with them instead sharing a comfortable silence as they headed in. They found Trinket's mate where they'd left her, still dozing away, and, much more surprisingly, Percy dozing against her.
Vex's laughter woke both of them up. Together they raised their heads, looking rather caught out. The bear only for a moment, before she lowered her head back down and returned to her nap, but Percy remained pink-faced as he hastily scrambled to his feet.
Trinket, inclined to nap himself after the day's exertions, headed to join his mate. On his way, he moved to nudge the mortified Percy, and give him a reassuring look. "He's glad," Vex told her husband, thought she didn't really need to.