Membership plugin

I want that our members register themselves as members on the site, provide information about email, telephone etc. This is managed by the usual regiser form i guess.

BUT, I also want them to register if they have children that are members, ie the children themselves cannot register because they are to young to manage this.

So with 1 registration it should show that they have 2 children for example, and we can reach them all with invoices etc.

Hope you get my question.

Regards