Do girls get their periods about the same time there moms did?

Sometimes. Every girl is different and unique in their own way. Some girls get their periods the same time their mom did and some just get their period on their own time. Little sisters may get their period the same time their big sister got her's, but it depends. So yes, sometimes girls get their periods the same time their mom did or a close relative. (sister, mom aunt, grandmother, ect.)