Kevin Tolwyn was "sent" by his uncle out to the Landreich, where he never resigned from Confed. He was a brevet Major after the Concordia went down, in which he was promoted during the War but didn't get the increase in pay. His rank to Major was probaly confirmed by the Senate after the War, but with the senior grade officers (Majors, Lieutenant Colonels, and Colonels) being driven out and RIFed out, he probaly would have a hard time trying to stay active duty. Especially when Admiral Tolwyn still had his share of political enemies.
Some time after False Colors, Kevin Tolwyn returns back to Confed, where he eventually becomes a Commodore.