Board Thread:Episode Discussion/@comment-3125844-20150731045049/@comment-1509826-20150802112834

Well its unclear at the moment, she never mentioned them (even after learning that being a grimm was hereditary) and said she was in foster care since she was a little kid.

So its seems likely they either died when she was very young, or perhaps they were forced to give her up, much the same way Kelly was forced to with Nick.