Can step kids claim half of my dads estate if my dad's ex-wife died seven years ago

My father was murdered on March 30, and did not leave a will. My sister and I are his biological kids, my step mother died seven years ago and her kids, my dad's step kids have had minimal contact with my dad for seven years and now that he died they want to claim half of his estate. One of the step kids filed like I did to be the representative of the estate. And was granted it after I did. I am going to take them to court cause I feel that they have no rights to claim anything since it's been seven years since their mother passed and I feel the ordinance of law should of granted my dad owner of her half of the estate after she passed. The warranty deed is listed as Larry Herrera and Flora Herrera, Husband and Wife, Which in my opinion is both were joint tenants of the estate until she passed and at that point the estate would of followed the ordinance of law and would of been giving to the surviving spouse who was my father.