There is no law about that.
I would say never
It's legal if they're brother and sister, maybe.
There is no law that says a brother of a certain age can not share a room with his sister.
it is not illegal for a brother and sister who are aged 5 and 2 to have to share a room in New Hampshire. The parents can however have them in different rooms if the space permits.
Latios and Latias is brother and sister Latias is the sister Latios is the brother if u seen the movie they share the same father
It should depend on the parents financial situation, with the economy today not everyone has the luxury of each having there own rooms, they're grateful to have a roof over there heads, if it is illegal then let the state provide the extra income to allow the provisions for everyone of the opposite sex siblings to be accommodated.
brother and sister
Well there are some laws that say a brother and sister can't share a bedroom, but I'm pretty sure a boy as young as 2 can. When he gets older you'll have to check the law where you live.
Of course it is legal for siblings of the same sex to share a bed! Not everything in life is legal-illegal--- thank goodness! Plenty of siblings shared a bed growing up and are none the worse for it.
Your brother's wife's brother is your brother's brother-in-law and your sister-in-law's brother. But he is not considered to be related to you. Usually you could just refer to him by his name.
It is not illegal for siblings to share a room. Age has nothing to do with it.
... will share a birthdate.