Is it normal my teen sons walk around the house naked, even when he's hard?

This is for dads with teenage sons at home.
I'm a single dad and I have three teenage boys who are 14, 15, 16 years old. We live in a small apartment and since it's hard to get any privacy, we're all pretty open with each other in terms of being naked, especially since we're all boys anyway. My sons are all very good-looking guys who are into sports and bodybuilding, so they tend to not be shy with their bodies and they actually tend to show off. They walk around our apartment shirtless a lot, and they like to go for runs around our neighbourhood without shirts on, which has caught the attention of quite a lot of admirers.

At night, my sons share a large bedroom with separate beds and they all sleep naked. I usually go into their room to wake them up in the morning and I see them naked on their beds. There are even times when I come in their rooms to wake them, and my sons have morning erections fully exposed and pointing straight up the ceiling, but they don't seem to mind that their dad could see it. They sometimes even walk around the apartment naked with their penises fully erect even if they know I'm just around and could see. They don't seem embarrassed at all and they don't try to cover it up. Being their dad, I understand that my boys are growing up and it's completely natural that they get erections, so it's fine with me. I guess over time we've just gotten really comfortable around each other, so to us this is no big deal. Does anyone else feel the same way, and have any parents seen their boys in the buff and do they mind?