Gaaaah... I really ought to keep track of what I've read better than this, but I'm just terribly disorganized in nature... Oh, but that's still no excuse. Anyways, this time I'm looking for aanga where a professor hires his university student to sort of be his housekeeper and take care of his son. They end up together eventually, and the son begins calling the university student 'okaasan' or 'mama'. Also there was a relative of the professor (also male and gay to boot) who made trouble for them for a while there, but it was resolved with that guy's lover returning.

Not sure, but a quick search lead to: Happy Yarou Wedding? Also, there are two categories of convenient size, which may be helpful: Housekeeper and Housekeeping.

"It's like love is a bonus in your life. Even without it, I'm just fine. I don't feel like pointlessly searching for it. You don't have to make yourself unhappy." (Ookami Shoujo to Kuro Ouji)

"Why does it rain?" - "To create drama." (Drops (Andou Yuki))

I'd concur that your description sounds exactly like Happy Yarou Wedding.
And the relative that caused the trouble and his lover have their own books as well as showing up in other books by the author. Unfortunately, I don't remember the main couple from Happy Yarou Wedding having much presence in the other related books but if you like stories that are interconnected this auther has several.

Thanks! Yes, it's that manga! I've just deplorable skills at using the search engine, tried typing yaoi and professor and college student, and it didn't seem to do the trick. Thanks for the tip!