It used to make me uncomfortable just because I was raised knowing it was illegal, but my eyes are so impure at this point it doesn’t bother me anymore.
The thing that bothers me is when they go the stepbrother/sister route. “Gasp! We’re actually not related by blood!” type thing. Like, it...
Go for it. Or don't. If there isn't sex nobody cares.
(Just kidding. Do whatever you want, but I'd recommend thinking about the personality of the lover, and whether you think it'd suit the way you write males, or the way you write females, better.)