My wife and I have had this paradoxical relationship with him and particuliarly me when I have baby sat with him. I seldom had problems with him until his mother came home or back to our house. Then, he would start to cry, wanting her to hold him. Now she comes home and he just smiles at her and continues to play with PaPa. She has both the look of relief and puzzlement with this new behavior.
Our second son was like that until his first year. We joked that if he had been the first, he would been an only child. About the time he turned 1, it was like a light switch was turned on and the monster switch was turned off. He became nice to Dad (me) and treated us like equal parents.
Say the monster switch has turned on and I will agree with you!!!!!!!!! We have yet to figure out how to turn it off.