I want to clarify this, If I may...The three sons are not blood related? Father passes away and leaves the home to his wife (step mother). That is typical in a marriage situation. But then she passes away and deeds the property to her own two sons and thus the original son is left out?
Interesting and completely unfortunate. The only thing that could be done is hire an attorney to try and get this house into probate. May or may not be possible depending on the specific laws in Oklahoma. Call a local attorney have a free consultation on this matter and see if they can help. Pushing this into probate would be your only option and would likely work out in your favor. The attorney can better advise you on that as States handle this different.