wait can we know more about your jean greyerl is des's daughter headcanon? i dont think ive heard this before and im really curious /gen
Oh my thank you for your question! I made this post terribly long ago that essentially sums up my thoughts, but I think I'll expand a little. Also I use they/them for Jean Greyerl.
Essentially, Targent is considered the largest military operation (that I'm aware of at least) in the world of Professor Layton. They have a lot of capital to back their organization and likely have their hands in a lot of projects (it wouldn't surprise me if they ended up backing Clive's Future London as well). The Labrynthia project seems like something Targent would want to be apart of. 1) it's such an insane premise, tricking hundreds of people into thinking they live in the dark ages 2) it's a convenient way to relocate and brainwash hostages.
If my memory is correct, I don't think Desmond ever says that Targent killed his family (please someone correct me if I'm wrong) but it's implied that they had something to do with why they are no longer around. Either way, Desmond fully believes they're gone.
Jean being Des's child just fits for me. They're approximately the right age, they're very intelligent, and there really isn't a whole lot of information given about their parents. I used to believe that either the mother or father was Des's partner, but now I think I lean more towards neither of them being Jean's actual parents. Jean being so willing to leave their parents and live with Belduke plus the fact that the mother and father are never mentioned again makes me think they were never real to begin with.
Anyway, that's just my own personal interpretation! You're welcome to agree or disagree, but it makes me happy to think about! Plus I like to think that after everything about the Labrynthia project is exposed, the Professor is able to help reunite the two of them!