In the house I grew up in, we were rather free as far as clothing goes. I think by the time younger brother was about 6 or 7-years-old, my mother would shut the bathroom door when using the toilette and he didn't bathe with her anymore. As far as girls in the family being naked in the same room together--that has never been a problem. The saying from where I'm from is "We've all got the same parts, right? It's nothing you haven't seen before." So, high school dressing rooms without private dressing stalls and community showers are the norm and everyone is pretty relaxed about being naked in the same room with the same gender. However, growing up my dad and brother still often sat around the house in their undies and on a hurried morning you might see my mom running around frazzled in her bra and undies and an open housecoat. We never felt weird about any of this and where I'm from, no one else would either. In Mainland China, people are VERY FREE about being naked around members of the same gender. When I studied there, the city I lived in had bath houses (most people do not have hot water in their homes) so once or twice a week you would trek down to the local bathhouse and some women spend hours in there, sitting naked, brushing each others' hair, scrubbing each others' backs (and other parts too!) and exchanging the day's gossip. That was a bit too free for me but I was not offended by it (never adapted enough to scrub anyone's backside, but...).
This is such a cultural issue and personally, our family is not shy (and at the same time we have proper modesty) about our body parts. And if anything, I think this has fostered a better sense of positive body image as well has kept shame about one's body and sexual parts to a minimum.