Though we never went to nudist resorts, my father was a nudist at heart (he'd grown up in a very prudish family), and he'd lecture us about how stupid it was for people to be ashamed of their bodies, or to feel like they had to cover them up all the time, even at home. So his rule was, if anyone wanted to be naked inside the house, that was fine. As I recall, nobody acted on this directly except Mom, who would sometimes walk around the interior of our house in her birthday suit, after her morning shower. We lived out in the country, so being seen through windows wasn't really an issue.
My sister ‘Rachel’ (three years older than me) sometimes used the tub with the bathroom door open, and she hadn’t asked me to leave when I came in to brush my teeth or something. So I had seen every part of Rachel except her sex itself (which I had no interest in seeing)… and I appreciated the fact that I knew what a girl’s breasts, hips and pubic hair looked like even before I started sneaking magazines into my room. But while the women in the magazines turned me on, my sister definitely didn’t… and so I had to agree that my Dad was right in saying that seeing people naked and feeling aroused were two different things.
I don’t know whether Rachel felt anything on the occasions when she saw me urinating (my grandmother was shocked when she walked in on one such occasion), or when Rachel saw me getting out of the shower, but whether she had one of her boyfriends available or not, Rachel never made a pass at me, so Dad’s rule hadn’t led to anything unhealthy there, either.
On one occasion, though, on a family trip in a large van, Rachel complained that she didn't want to change clothes in front of her brothers. (She'd gotten muddy outside, and Dad told her that because of the curtain behind the front seats, no one outside the van could see her.). When he heard that that wasn't the issue, he got mad and said that maybe our family needed some periodic "no clothes allowed" sessions, to get get us past our silly attitudes. I thought it was a dumb idea, and Rachel objected vocally, so he never pushed it. He also dropped an idea he had later on, that it would be good for Rachel to let me inspect her body, before I started dating (at about age 15, for me.). Rachel and I both responded with disgust and basically said, "Not going to happen."
I guess he'd never thought about clothes in terms of marking some very reasonable boundaries, rather than a product of shame.