Is it illegal for a 10 year old child sister to share a bedroom with a 12 year old brother for about 6months

I know of no florida statute that makes this an illegal act, unless bona fide mental distress can be documented. Instead of taking advice through random Google users i.e. the previous commentor, who should provide at least an applicable statute rather than a personal belief, you should ask svu detectives this question. Full disclosure I was one of those detectives for 4 years before transferring to another investigatory bureau.

Yes its illegal