I actually quite liked the 'landlady' and 'fellow tenants' thing. Incest does nothing for me, I think it's mainly a trope because it makes it very easy to have a reason to have 3 to 4 hot girls in the house you can creep on. ("mom" and "sisters" and "moms wild sister" for example). Milfy city has Caroline, BADIK has Bella, Midnight Paradise has Joyce, they're just my type. Stunning with some attitude but generally a good heart. Now 2 of them are supposedly related to you, but if Caroline was the girl next door I'd be creeping into her window still, If Joyce was the lady I cleaned the pool for, I'd still want to clap those cheeks. And I'm not less attracted to Bella because she's not related to me.
Basically, I'm attracted to personality, looks and certain sexy (to me) locations/positions. If I can fuck a big breasted stunner in the shower, I don't care if she's my kid or a stranger I walk in on as I check the pipes *wink wink*. I don't consider the relationship the MC is supposed to have with the character, I consider the feelings I as a person have towards a character, and none of them exist, so I don't consider any of them relatives.