I am a notary, can I notarize a document for family?

It is not a good idea, also how close a family member.
And I guess what document in regard to marriage is it.

No. At least my state you can't. According to ethic rules, we "should" not notarize for family or friends. Not saying it can't be done (unless you have the same last name), but just remember... you are the party that will be responsible for it all.