I found 181 Griffins in the National Parks service listing of soldiers from Texas in the Civil War.
In the 11th Texas Cavalry there were a Benjamin, an O.D., a James , a T.J. and a T. l. and one Z.
In the 27th Texas Cavalry There are a D., David, and a Benjamin. Benjamin and David were probably Kin. Look in the Census for 1860 for Benjamin, Owen and David in Texas. You may find the links your need. The difference between 34 and 18 could be father and son. Particularly if the son lied. the census would help there. Go to the County and look at soldiers joining the 11th and Benjamin Griffins Company. The National Parks Service sometimes slips up on fathers ans sons with the same name. I will keep looking.