@Yukimusha
Isn't the family written unrealistic on purpose? I doubt it reflects any real beliefs on the author's part. There's also no way so many experienced gamers would suddenly go crazy about a few kids joining the game, let alone their big brother. It's just the setting of this series, all of it.
But then again, this is a manga where someone fights slimes barehanded...
Why would three 13 year old have any shame when beside an older brother that make cloth for them? It's not the first time and each time author's put these talk it make things weirder.