I've always been extremely close with my dad and 2 brothers. He was a single parent when I was growing up and we had a small apartment so we always saw each other naked. My dad was always somehow hotter than other dads I saw, like my friends for example; my dad was fit and theirs were fat, but I never had a desire to sleep with him. I'd never forget this one time though when I was 14, dad came in our rooms to wake us up for school with a huge hardon (he sleep naked), I was like dad wtf...he just looked down and said "oops didnt realize haha"...From that point on I took it as a challenge to see what I could get away with. So for breakfast one day, I think I was 15 or 16, I walk into the living room while he was watching T.V. completely naked with a boner and sat down at started watching also. He looks over and says, "Uh son is there some point your trying to make". I was like nope, next thing you know my brothers come in and are like "Dad y does he get to walk around naked with boners", dad was like "fine if you wanna walk around naked with your dicks hard be my guest, just dont scare the neighbors". We all looked at each other and laughed. After I realized my dad was relaxed about it, I never did it again. Me and my dad are still really close even though I'm in college now; when he drives 5 hours to see me every other week we always sleep naked together.
P.S. My dad isn't gay or bi he actually has a GF now for 3 yrs but he's not afraid to be nude or physically close with me and my brothers, but nothing ever sexual.