Distant Relative
A distant relative is someone that you can carelessly have sex with, because they are your family they can't really hate you, no matter how bad you are in bed
Example:
girl 1: Why did you do that to him??
girl 2: He's a distant relative ;) so it doesn't matter
girl 1: Why did you do that to him??
girl 2: He's a distant relative ;) so it doesn't matter