My step-mother passed away in December 2005 (cancer). My father currently lives in the the house they have shared for 20 years. She has 1 son from a previous marriage who lives out of state. When she passed away, the title to the house was in her name only. There is not a will. Again, they were married for 20 years and lived in that house for 20 years. She had lived in the home with her son approximately 10 years prior to my father being married to her. Now, her son is saying that he has the ability to take the home from my father. Does he have any claim to the house? The house is located in Missouri. Your input is much appreciated.

Consult an estate attorney. I would say the son cannot do that. If there is no will, the intestate statute controls, and usually most states will give a surviving spouse a life estate in the home. Also, the husband probably inherited a share in the home- what share depends on the state intestate law.