Jesse is currently the only child of his parents, but the Lin family is very large and relatively powerful and influential in the Dome, and he has dozens of cousins. As the Lin family is also very close-knit, it's almost like he has dozens of siblings! Almost.
Unlike most, Jesse was born to a level of privilege that many are not fortunate enough to have within reach of them, let alone be born into it, but the difference between him and most of upper society is that he knows it. With as many cousins as he has, and as much of a free-spirit as he and his cousins often are, they've brushed elbows with poverty, oppression, and the fact the war with Andasca isn't a war so much as a genocide many, many times.
He went through school, actually quite happily because he had many questions about many of the things he saw closer to the Outlands. None of them were answered. He went through classes in Erebos University, and then he joined the United Republic, in the Medical department. He had dreams. Most that walk through the Tower's doors do.
At present, he's been helping a friend with a slightly might be kinda illegal pet-project. Meanwhile, his cousin's becoming a handler to save this kid he met in Pyxis. Yeesh. Gods have mercy on them both because they're both fucking nuts.