I was going to say 10 or 12, so we’re in the same ballpark.
From the alleged entries in the left behind diary, that seems way way too old for a girl to be presumably naked in a shower with a naked grown man, daughter or not. Some families may do family nudity casually, such as nude saunas I guess. Perhaps a cultural thing in areas of the world? I don’t believe that is anywhere near the mainstream here in the U.S. Thoughts?