He is a boy
Since we know for sure you have mixed genders, it's important as I said previously to prevent breeding in any way possible. Additionally, while right now they may all get along, as they grow and become more hormonal, one budgie may become the "odd one out" and be picked on by the other two, or two of them may try to be friends with the same budgie and stop getting along with each other.
It may be a good idea to house them separately starting now. That way, you can keep the two sisters together and then have this little guy in his own cage near them. If they all get along you can certainly let them out for supervised out of cage time. He won't be lonely with his sisters in the room, and additionally you'll be able to bond with him as well. The other reason is that if you wait until they potentially don't get along to house them separately, then the flock dynamics could have been changed to the point where one girl has decided she wants to be friends with him and not her sister, which then makes the situation more complicated as you will have to by hypervigilant about accidental breeding.
As I said, you don't
have to do this now but personally I think it's a good consideration to make while you can still have some control over the dynamics of your trio.
They are adorable and I can't wait to see more of them! Any name for this little guy yet?
