It might be, for people like sisters, or people who get it from their parents. My best friend told me that his mother and his aunt, (sisters) are both very ticklish, so hereditary ticklishness is quite possible.
I couldn't say either way on that one.But I do know that being "into" tickling is not.To my knowledge, I'm the only one amongst the "kinfolk" who's turned on by it.Don't know about relatives from way back when, but I doubt it.