Doesn't look like he inherited anything from his brother. A life estate evaporates when the holder dies.  But what actually happened?  Did Mother give a life estate to First Son, then the remainder to Second Son?  Then you would go back to 2006 FMV at Mother's date of death.  Part of the value goes to the life estate, based on age of First Son, and the rest goes to the remainder of Second Son.  The tables changed in 2009, so make sure you use those from 2006, if it really matters.