It depends. First, is the trap cute? How cute? Next, is it my actual little sister or one of those unrealistic anime ones? And what kind of unrealistic one? A cute trap will not win against my little sister unless he's really really cute. And even then, he might lose to an unrealistic anime little sister of my liking.
I like traps but my siscon instincts will take over.
Edit: It seems I have mistaken its definition. I am not into incest. I'm more of an overprotective brother if anything.