Had this in my head for a while now, and finally decided to do it XD
In case it's not completely obvious by now, Morty is bisexual. When he was a kid, he was confused about his sexuality, and tended to be a loner, which is why he bonded so well with ghost types (also because he's an empathy). Morty finally became comfortable with his preferences when he found himself in love with Dantes. That romance was short-lived, of course (Dantes is completely straight XD), but Dantes DID encourage Morty to be true to his feelings, and commended him for being brave enough to admit them. And ever since then, Morty's been A-Okay with his sexuality~
By the way, Mortimer's specific preference is blue-eyed brunettes. Man or woman. That's all he ever dates XD
Crystal doesn't have a problem with Morty being bisexual, by the way. She'd just rather not think about her dad in a gay relationship
Morty (c) GAMEFREAK, Nintendo, etc.
Crystal, artwork (c)