I could see, if a superhero had designated teammates as guardians for their minor child, the teammates winning against family members if they pointed out that the kid was almost certain to have powers, which could be dangerous in untrained hands.
Indeed, if a child manifested superpowers, it might be necessary to have him put in the custody of superpowered people who could constrain his ability to cause harm, and train him (and probably have a more durable home than most). What this would do to parental rights could vary a lot. . . especially depending on whether the parents can cope with their kid's superpowers. (Come to think of it, that would depend a lot on where powers came from, too.)
On the minus side, if they are sidekicks -- are they child soldiers in violation of the Geneva Conventions? not to mention child labor laws.