This is a complex issue and depends on many factors. Did his father have a will that was probated? The first step to understanding your step Dad's options would be to contact a probate attorney to look at the issues. Go to the State Bar of Texas website to get a referral to a probate lawyer: http://www.texasbar.com/Template.cfm?Section=Member_Directory
This is a legal issue and your best source is a licensed attorney to unravel it for you.
Tory Sartwelle, Realtor