Not at all a fan of Martin. The developer basically cucks the player every time he returns Martin to the game. As disruptive as Martin can be to game play, he should be an opt in / opt out sort of thing.
I have no idea what the developer is doing by forcing us to pretend we like Martin; he's toxic to his own family. There's plenty of drama and conflict here without him.
If sharing relationships are supposed to be about boundaries and respect, Martin fails on both counts IMO. Unless the developer allows us to end Martin once and for all by letting the MC beat him down and exile him from the relationship, I'm really disappointed at this plot (re-)turn. If the MC catches Anna cheating on him *again* I don't see why the relationship should continue. On my playthrough, they nearly divorced once already because Anna would not respect the MC's boundaries...
If you want him on your route, that's fine for you.