Boy wearing sisters bra and panties?

Yes, it's ok. And it doesn't mean you're gay. On the other hand you should really get your ownor just save a few pairs of her panties and Bras in your secret spot or whatever.
Be careful not to get caught.
The feeling of pulling her panties up and feeling them arrive snug against your d**k, her crotch against your crotch.
The straps over your shoulders, her cups holding your tiny little breasts.
Very very comforting...