Just a thought ... you said they were "brother and sister" ... do you actually know what sex they are, or were you just saying that because of their names? If I remember correctly, they have to be a certain age before you can tell?

The reason I ask is ... if your brother has a rooster, and one of these babies is also a male ... he will more than likely have serious problems when they grow up. One rooster likes to have the hens to himself, a little harem. Depending on the species, rooster can and do fight to the death. I remember my grandma's roosters fighting until all were dead but one.