I get what you mean tbh. I didn't have siblings but this sort of stuff happened with friends when we were kids. The fascination with bodily functions and just being chill about running around naked and whatnot seems pretty standard. We weren't completely ignorant about sexual stuff but at that age it was in the spirit of curiosity and lulz. So I don't think OP needs to worry about it.

Also I can't help rolling my eyes at the general over-use of Freudian theory in everything.