Remember in GF2 when the young Vito is at the play with I think Tessio and Tessio's girlfriend is on stage and Tessio says to Vito "Look at her isn't she beautiful" and Vito says to him, "Yes she is, but their is only one woman for me." Vito was very dedicated to his wife and his marriage. I think Vito looked down at Sonny for not being faithful to his wife. Vito knew Sonny was cheating on his wife at his daughters wedding and I think he was very upset with Sonny for this.

DS