At 9 years old he probably is not "big" enough for anything but a youth sized cup. Be sure to get the curved kind of cup, not a flat kind, especially if your boy is playing catcher!!!
Sports cups come in different kinds and brands. A sports cup should fit the 13 year old boy tightly. The sizes come in small medium and large. The size will need to be determined by trial and error.
baseball.
depends on how thirsty you are
whatever fits, lol
34 size , c or d cup ..
Everyone develops at a different speed but I would say an AA, A and maybe a small B cup size is average size for 11 year olds.
A 13 year old boy can wear a bra if he wants or needs to. A boy wearing a bra is not a common thing.
10 year old girls are not really supposed to be wearing any kind of cup size.It's best to wear training bras or sports bras...But if a 10 year old were to wear a cup size it would probably be a 32AA...11,12 and further that's when you really start to wear a cup size.
could be anything but most are about an aa/a cup to a b cup
It depends on your family history and weight/size. For example if your on the skinnier size you probably won't be very developed. But that is completely okay! If your on the chubbier side you could be a larger cup size. If I were to pick an average cup size it would probably be 30A-38A for an 11 year old girl.
That is going to depend on how big he is both overall and his genitals.
That depends on the size of the girls breast and chest measurments.