Honey I wish I knew how to help you..I wish I knew how to get HIM involved with cleaning around the house! Maybe offer both of them an incentive. They get to pick an activity of their choice for doing chores.
I'll be positive and suggest that you give him LOTS of praise for doing what he naturally SHOULD be doing! But praise works! I tend to nag and he hates that, but I feel like we both work, we both created our children, so we should both help out. Doesn't always work that way. But there's that old saying, "You get more with honey, than you do with vinegar...!" So don't nag, be sweet.