Pondering the Family Tree

As part of G's recent history lesson, we made a family tree booklet, a page of pertinent information (e.g. birthdate, birth place, parents' names, siblings' names, etc.) for each person. When filling out Drew and my individual pages, G asked for our marriage date and was puzzled when I responded, "It's the same as Daddy's." I was so taken aback when she asked, why, that I simply didn't have a ready answer for her. (Go ask your dad?) Where did I go wrong as a parent? :)