How do I get back family heirlooms that were to be returned to to us upon death of my grandmothers new husband?

If your grandmother's will gave him the property then her will usually can't control what happens to the property when he passes. That is up to his will. If a trust was formed and the property put into a trust then that would control. If a contract to make a will was created then you could use that. Just given what you have said here though it sounds like there isn't much you can do. Have a probate or estate attorney look at what paperwork you have (your grandmother's will, etc) and see if there is any legal recourse available according to those documents. Based just on what you have written here I am doubting you have any legal recourse.