(Age/2)+7
There's a reason for this rule. I have seen how different people around 20yo are vs people around 30yo. Afaik they are legally allowed to do that. The bigger the age difference the higher the chance that there is grooming or manipulation involved. 10 years is too much.
Look, no one should die but that age rule is very good to understand ethical boundaries. I'm sorry, but if a 30yo dates a 20yo it will always be weird to me and I will question what is going on behind closed doors.