Beckett K. Howell was born in 1840. He obtained a commission as a 1st Lieutenant in the U. S. Marine Corps before becoming a 1st Lieutenant for the Confederate Marines. He was the only Marine assigned to the CSS Alabama. He was a close friend of Captain Semmes as well as the brother-in-law of Jefferson Davis. He was the brother of Davis 'wife, Varina Ann Banks Howell. He was promoted to Captain in 1863. After the war he returned to his home state of Louisiana and died in 1882.
I'm sure Howell did well enough for Semmes as the commander of the Marine detachment on the Sumter that he kept him around on the Alabama... but with no Marines on the latter ship, his position was a bit anomalous...