My husband and I train together. We usually follow the same diets too. We do a few different exercises in the gym, but we're on the same schedule, so it works out great. We're even on cycle together at times. Our lives are so intertwined, living together, working together, lifting together, it just makes every day go smoothly. Training together is great because we get to share out successes and the other one understands. We can be supportive when things aren't going as planned. We can push the other when they need it.
I've only been training for a year, but my husband has trained off and on since he was a kid. When I was younger I didn't really understand his need to go to the gym 4 or 5 days a week, but I never argued with him about it. He did his thing and I did mine. I'd compliment how he looked, I'd make sure he had food, and be really patient when he was trying to find dress shirts for work or get fitted for a suit. LOL