I just found out that my friend's brother was caught with his pants down with another boy in his room, is this a normal activity that young guys do as I never did this.

It can be just simple experimentation, it is completely normal for anyone to experiment with someone of the same sex or to even look at what they have and compare to see if you are "normal"
Not everyone does it, and it's all just very normal

How old are the kids in question? That plays a large part.

Younger kids will explore. It's not uncommon for them to be curious if someone else has the same parts they do. It's not really sexual. It's curiosity.

If these are two teenage boys than this has gone from innocent exploration to something sexual. Not that exploring your sexuality is a bad thing, but sexual exploration, touching, or anything beyond that, should not be done in the early teen years IMO.

So yes, a lot would depend on the age. At least that's my opinion. :)