We don't live with our in-laws but we used to. Right after I gave birth before my husband went abroad, we stayed there for several months. We just contributed a portion for each of the bills—water, electricity, grocery and other stuff. If we go out as a family, we would also bring my in-laws. We didn't pay for rent because they own the house.
Actually, I think you should be talking to your spouse about that. As a child of your in-laws, who, I suppose, are already aging, the responsibility is at your spouse and you can't keep him from that. After all, they are his/her parents. If you think things aren't fair when it comes to partition, reach out and talk.
Anonymous