How to give child blog user right to edit their blog's other users

I want to make child blog admins enable to edit their users porfiles.

For example, there’s a child blog and the admin is “Papa”.
And “papa” has his users “mama”, “John”.

Papa wants to edit the profile of mama and John.
But by default, Papa has no right to edit their profiles.

Is there a way of chaging capability of changing child blog admin?

Thanks.