As we saw, Michael was keeping his family at a distance at Connies wedding. If he'd been married at that time, he'd have been even more aloof from his family,
But, as a dutiful son, he went to visit his father at the hospital. There's no reason for me to think he wouldn't have visited Vito if he'd been married.

The key event in the Trilogy is Michael finding no guards on Vito at the hospital, and Mac slugging him. Those events set him on an irrevocable path--it awoke the dormant Corleone in him. I'm guessing that, even if he were married, he'd have wanted to kill Sol and Mac--to protect Vito and for vengeance.