J.P.
If she is happy and he treats her well, then be happy for her and let the family know that you are accepting of the age difference. My husband is 11 years older than me. We had some road blocks with my family at first that were stressful on the family relationship. We have been married for over 11 years and have a beautiful daughter. My family loves him now, but it would have been nice for them to have accepted him earlier and saved us all the stress.
J.