For me, I have a skinny husband as well and what I do is just bulk up his meals. I also remember that I shouldn't try to match him in what he eats. Some days, he even eats 2 dinners, one around 6pm and one around 10pm.
Anyway, an example of what I do is give him larger portions and for a while, I wasn't eating a lot of rice/grains so for example if I made an Indian style dish, I'd serve his over rice while I'd serve mine over green beans. Now I'm eating more grains, I reduce the other portion of the meal for myself.
You can't out-exercise poor eating habits.