Curious Krypton Customs: Kissing Cousins

There is an oddity in the universe of Earths One and Two in that Kryptonians had different perceptions of familial relationships than due typical humans. 

An instance was played out early in the career of Kara Zor-El who, as Superman's secret weapon was also the only perfectly compatiable mate to her cousin. And yet, this would not have worked emotionally given their brother-sister relationship. Such was not the case when Kara Zor-L met this same Superman who was unlike her own cousin, near her age range, and thus quite appealing to Power Girl who unlike Supergirl had more limited options as for as Kryptonian couplings were concerned, given that her Kandor on Earth-Two was in virtual reality unlike the very real bottled city of Kandor on Earth-One with its scores of eligible Kryptonians for Supergirl to select from.