Plot point question: should Ekon's brother be dead, or working for Eagon?
Depends on who his brother is as a human being.
Shaharanian folk, by nature, are proud people. And, coming from a culture where strength and loyalty to the Clan take priority, most from Shaharan would sooner die than become a flunky for someone like Eagon who is honor-less and an all around douche.
But, if his time in Veilbrand had any sort of cultural effect on him and any part of his personality changed there's always a chance he could have become a flunky for Eagon. So, it's up to you.