Short answer: Find problems and fix them. Or at least, get other people to fix them. He's a Do Good'er.
Thomas is the hermetic equivalent of an upper middle class, computer geek, an only child raised in a one-income household, who has suddenly discovered that the world doesn't revolve around him and that Evil hasn't been vanquished yet.
There's two catches to this snotty brat's childhood dreams of winning the world record for Most Nachos Eaten While Watching Showgirls: the first is that he was raised by the hermetic equivalent of the Mormons. The second is that he's too smart not too understand that he has the power to do something about the world he sees around him.
I've designed him to be just past the precipice of change. He has spent his entire life thinking he was safely behind the glass window. Then, about a year ago, he was looking through his glass window at a Faerie Revelrie, and was shocked to see something look back at him. What's more, it yanked him out of the window and into the real world, and has cursed him in such a way that he will never be able to sit behind glass again.
A poorly chosen job at Durenmar coincides neatly with joining a covenant that has a remarkable book, to give him some tools most magi don't think of. Mechanically, I want to spend some time thinking about Intangible Tunnels, Penetration, and new ways to fight evil.
As filius Gregarius, he has basically inherited the same job his pater had, by joining the Path of Seeming. This job is, as near as he can tell, to be the translator and sock-mender for every Criamon who walks by. Which would be really demeaning, if this people didn't earnestly need his help to keep the universe from spiraling down the toilet. Oh, sure, the others of his House might talk grand talks about the Hypostasis and Axis Magica, but at the end of the day, it's about being decent to one another because we've all got souls, yeah?
In the very short term, he's going to arrive at the covenant, discover his curse (and struggle with it), while discovering that the covenant has much bigger problems in the form of Duncan. The discovery that he's not the center of the universe will spur him to action, and he'll start looking for Duncan.
Then, like the old 70s episodes of The Hulk, he'll find people who need help everywhere he looks. And he'll help them, because that's how he was raised.
All this is going to happen against a backdrop of a terrible home life (-6 penalties to interact with his wife), disgrace amongst his religious peers for "choosing" to marry in the first place, and sheer dismissal by the greater Hermetic community. Not to mention all the potential legal troubles he's ripe for.
In a similar vein, Janet is ripe and eager to react to the world of the saga. She's young, naive, full of potential and too stubborn to let herself be beat down. I want her involved in other people's stories and reacting to the setting for a while -- no stories centered on her until the character "finds her feet." The covenant needs a lot of help, and she's got the potential to be any part of that solution -- assuming her demon-fueled pride doesn't end up destroying us all.