User blog comment:Merganafan23/Character ages/timeline/@comment-24.26.233.208-20120805002001/@comment-5364525-20120805003201

I think it was rather likely he hid her parentage because she was the product between Uther's affair with a married woman. A woman who was married to his best friend, no less. King or not, that would have been a rather black mark on his honor.