I'm clutching at straws here but I have a strange feeling the hobo is Lena's biological dad. I think Lena's mom was caught cheating on Charles (the hobo) with Seymour. Charles found out, left Lena's mom, she ended things with Seymour, Seymour ruined Charles' life as payback. I mean he does ask her what her relationship with Seymour is. As for why he doesn't just tell her he's her dad, maybe he's just ashamed to admit he walked out on her. Which checks out since Emma says he's reserved about his past.
And Seymour's reasoning for lusting after Lena could be a sick and twisted way of exacting revenge on her parents? Sponsoring her and enhancing her career while simultaneously corrupting her so that she'll want him and then once she relents, he reveals everything then gives one last fuck you to her parents and is all "I did more for Lena you ever did" or something along those lines.
Idk just a crack theory.
You're not crazy. Been saying this since Chapter 9 or earlier. Not as much with your specifics. But definitely Seymour being interested in Lena's mom & destroying her dad (the bum) out of vengeance/jealousy or as a way to eliminate the competition. Hence Seymour's bizarre obsession with Lena who is otherwise just another dime-a-dozen hot chick to a triple-digits+ millionaire. A do-over he can control to replace the one that got away.
Quite a few of us have been speculating that Seymour was into and rejected by Lena's mom for quite some time too, since nothing else explains such an obsession (other than a few people's incorrect theories that Seymour is actually her father. He's not, for a variety of reasons, proven in the game also).
Bum = Dad is a little less definite. I'd put down $10k on Seymour as Lena's mom's rejected suitor though. Will likely be revealed during a hospital visit or a bill paid when Lena's mom falls ill. Unless Eva starts reading these posts and cares enough to change things for seeming too obvious. This is one of the few "coincidental" plot-points I'm fine with though, since it's not really so coincidental and more of a calculated move by an obsessive control-freak. I.E. more plausible than many of the convenient "cuz red string" coincidences in the game.
It is not(!) proven in the game that Seymour isn´t Lena´s father! Seymour might never have been told by Lena´s mom that he is the one and he tells it to Lena the way he is aware of, that he has no children, but the way he treats Lena on most path variants hint strongly that he suspects she might be his daughter.
Come on, Seymour is very much simping after her, he could recruit established supermodels without problem, but he chooses Lena and can be quite lavish in his attention to her. It might have started as a chance encounter, but Seymour seems to suspect now Lena could be his child. And considering how bad her mother treats Lena most of the time, hardly as part of the family, is another hint that she is probably Seymour´s daughter.
Remember that Syemour got rejected for dubious reasons by a woman? Lena´s mom might have been involved with Seymour, cheating on her husband and when she got pregnant had to pull the plug. She would clearly know that Lena is Seymour´s daughter, a part of her life she wants gone. Lena is treated by her mother like an ATM and not much more. She is on the very outside of the family, her younger brother, a waste of space, instead get´s treated with lavish love by their Mom.