Harvest moon another wonderful life why did my son leave?

Sorry but I knew what was coming as soon as you said you had a son with Rock. Unfortunately that was not a glitch that happens sometimes when you marry him. See your child's personality depends on who you marry. Rock's kid is a spoiled ungrateful brat. And there is a good chance of him just running away like that. I've never heard of that happening with any of the other guy's kids. There is nothing you can do, but if you start a new file you might not want to marry Rock.