If Peter was single, how did he have a mother-in-law? (See Matthew 8:14.)
He may have been widowed. It is implicit the disciples left their former lives to follow him and then bring the Good News the nations.
But even married couples singled out for mention in the Bible hardly ever remain stationary. And I bring that up to say they weren’t living out the American bourgeois middle class realities that people now commonly associate as inseparable from marriage. It’s a lot deeper than that, and perhaps that’s why secular therapists or Christian counselors overly shaped by fickle cultural realities are out of touch with timeless and eternal concepts that need to be at the center of marriage.