I've the same opinion that @Sara2001,I feel it very intimate.
Yes!
Ines It would be nice, and for sure it would be nice towards my brother, but... she has the choice!
Maybe,as they started to talk about it,they both have thought about her wearing one,even if not discussed it together.What would you tell her if she asks you about chastity belts,and the possibility for her to wear one?Should it be her who asked for it,or can your brother ask her to,and she can accept or refuse?
How this situation would help you if she doesn't wear one?