Two stories in one, the first book is Alien Debt.
This is the story of how Bran and Rissa met and negotiatied with the aliens whose downed ship gave UET their access to space and allowed them to take over a world.
When they found these people - who they were afraid would hold a grudge for that long-ago incident, they found themselves in the middle of an Intergalactic war and being asked to choose sides.

Rebel's Seed:

The Children of the Rebels are trying their wings. They find themselves in the middle of adventures that will test their mettle and perhaps take their lives. ( )