The "little brother" may not necessarily reject a sexual encounter with a woman with whom he has developed a "fraternal sibling" relationship, but it is not the primary motivation for initiating or continuing the relationship and generally not the desired outcome.
Generally smaller. Quite annoying at times and seems to take great enjoyment in copying your everymove.
Felix: "Mm I'll have a strawberry icecream with walnuts and chocolate chips please."
Younger Brother (Is allergic to nuts): "Can I have a strawberry icecream with walnuts and chocolate chips?" (Innocent smile)
Felix (sigh): "Ehh..." (gives up)
-Result: Little brother in hospital and Felix grounded-
"Ahh! Now that was some good stuff!"
"Whoops. Little brother."