By the time her story was written down, Margery Kempe wasn't all that into her hubby anymore (she prefers Jesus), so we don't know all that much about him. But here's what we do know. For one thing, Kempe initially thinks John isn't highly ranked enough socially to be a part of her family through marriage. Well, that's great.
We also get a full scene between Kempe and her husband when they are travelling to see the mystery plays in York. At this time, they've already been abstaining from sex, and this is uppermost on John's mind as they start to chat. John asks Margery an odd question:
"[...] if there came a man with a sword who would strike off my head unless I made love with you as I used to before, tell me on your conscience—for you say you will not lie—whether you would allow my head to be cut off, or else allow me to make love with you again, as I did at one time?" (I.11.58)
Can you guess what Kempe says? That's right: she's all, "I would totally let him cut your head off." John is so angry at Margery's response that he accuses her of being a bad wife, and hints that he will take what he wants no matter what.
But he doesn't. In fact, John even consents to Kempe's request to take a formal vow of chastity. Kempe, of course attributes his change of heart to God's work.
We can't know what John Kempe thought of his wife's experiences and choice of life, but we do know that he had a hard time sticking by her side at all costs when she acted up in public. When they are in Canterbury, he abandons her when her noise becomes embarrassing—and after twenty years, Kempe remembers this incident enough to include it in her narrative.
Kempe tells us, in a roundabout way, that at some point she left John's house in order to pursue a truly contemplative life. We know this because she's really unhappy when he falls down the stairs and cracks his head open, and she has to interrupt her schedule to take care of him. It's a great irony that in this time period, in this book at least, it's the male voice that's silenced by the female perspective.