Looking at it from the other POV, if a bunch of related women are all hot, men always think about shagging the different sisters, or a mum and her daughter if the former has aged well, so why not women? When she's 84 and has no teeth, she'll still be able to reach back and remember the time as a slutty teen when she could have any number of guys. Being young doesn't last very long, so personally I think its a good idea to make some memories you'll look back on with pride lol.