Can boys wear bikini tops?

Only if he has moobs.

Why in the world would a boy want to wear a bikini top? Aren't boys silly enough without wearing silly ass stuff like a bikini top?
Now a man, secure in his masculinity could certainly pull that look off, but again, why would he want to?

queer as fuck, cock slut boys can yes.

Wear whatever you feel like, just be prepared for the comments from others who will find it amusing to ridicule. Unless you learn to hide things with additional clothes, flannel button up shirts, hoodie sweatshirt, etc.

I sport a mangina at the swimming pool, no top or bottom. The kids get to watch me from behind.

I DO - I`m a 35 guy !!

Now there's cross dressing, and just being ridiculous. If you want to wear something over your chest in the pool just wear a shirt like a normal person.