Personally, I’m fine with it as long as both parties have cosent, though only for people of similar age (siblings, cousins, etc.). For people with bigger age differences (>=10), I’m afraid there will be the so-called “power imbalance”. I also don’t really like age-gap non-incest relationships for this reason. Maaaaybe if they’re old enough (30+ for the younger one AT LEAST) they’ll have enough life experience. Being too young will have a bigger chance of power imbalance due to huge gap in life experience.

And inbreeding, well, my first opinion is hard disagree. But if their gene is far apart enough to be safe, then maybe it’s fine. The main reason is I just don’t want people in incestuous relationship to take more chances of having a disabled kid. Though like what other commenter said, this could lead to disallowing disabled people from procreating. I don’t like to talk about this stuff since it’s a very sensitive topic for disabled people, but personally I’d like to minimize the chance of passing defect genes through alternatives like adoption, etc. I’d like for the future kids to have a better life than what we currently have. Definitely not something that should be passed as law, as I’m very sure it’ll get abused to hell.