Huh??? No it's not.Dating someone the same age as your younger sister is weird that close still to puberty.
Well my point of reference is puberty, and being too close to puberty, so if you were 15 would you date your 13 year old sisters 13 year old best friend?
Closer to and past 20, it's far less disturbing, but the nature of young girls is that they hang out with other young girls who think, speak and dress like they do, so sleeping with your sisters best friend is really just a dry run for sleeping with your sister.
Especially if they go to the same hairdresser.
Seriously, how dumb is he? That Josh kid does not have a brown mother like he thinks he does. If you were that bugger, how can you not suspect that you were switched at birth?
Switched at Birth.
Now, that was a damn good show.