As an owner of two male litermates
What you described is part and parcel of normal dog behavior
They are finding out who is going to be the alpha dog
The humping is even part of the whole process
Dogs will hump things that they feel belongs to them
which is why some dogs hump their owners
But unless they are hurting each other .... where there is yelping involved
I'd leave it alone
It might sound loud and scary but they are just play acting
false bravado you might call it