Great job Brendan, now all you have to do is think of a story

Wow, that's really good! Now I want to know what happens to Inesdar next!

As for story ideas, I don't have any for you now, but it does have a lot of potential... if you wanted to later, you could even make a prequel with this!

That sounds great! I would love to read whatever story you come up with for this.

That's a pretty good plot! It sounds like it took a lot of thought to come up with. But I see your dilemma. That's a lot of history to cover in one book how do you know where to start. Perhaps you could split it into a series or even write it in the present time with flashbacks to fill the reader in on the whole story.

That's just a thought though. I hope you can figure it out. I would love to read it in book form sometime!

How old were the brothers when they were separated? This would play a crucial role in how their fighting on opposite sides affects their relationship. If they were separated at infancy and never really knew each other, then you could have them share this fierce emnity until the escaped Inesdar (I know he escapes after 10 years and it would take longer than that for the boys to mature from infancy, but maybe his search took him another 5 to 10 years) finally finds Tarnim and reveals the identity of his archenemy, or Inesdar in his search for Adreal and Tarnim could be captured by Jerimas and realize his identity, escape from him, find Adreal and Tarnim and tell them about Jerimas. Or a thousand other possibilities unfold from the fact that two brothers separated at infancy are now fighting for different sides.
If they were separated at a later age, then you could make it even more interesting.

Another question to think about: how did Jerimas come to fight for the enemy? Just because he was captured by the Ra'thak doesn't inherently mean that he would join their side. Why did they even keep him alive instead of killing him with the others? The age he was captured at would play a key role in figuring out this story.

Does each brother know the other is alive, or do they each presume the other is dead? This too would open up a lot of possibilities for where to go with your story.

In your "Premises" post you mentioned that the younger brother (Tarnim) fought for the good guys while the other brother (Jerimas) was the "absolute leader of all the human forces of Merhios". You never implied that Tarnim had a leadership role. You could work out a plotline where he's just a lower-ranking soldier who gets captured for interrogation by the head human Ra'thak who discovers that his captive is really his younger brother.

It really sounds like you've worked out a good backstory foundation to build your story on. Just remember that not all of it has to come into play in the actual story itself. Think about Tolkien's use of the material from The Silmarillion in the LOTR. He didn't recount it all, only the parts that added to the story he was currently telling. The direction you take with the story depends heavily on what parts of the backstory you're pulling into the future. Let me explain: do you want your story to be mainly about the two brothers fighting on opposite sides? If so, not all of the backstory needs to be told (i.e. - a lot of the earlier parts about Inesdar would not need to be pulled directly into the story) Do you want to include into the story the element of Inesdar finally reuniting with his cousin and her son? If so, more of the backstory would come into play; but even then, it would not all need to be told.
These are just some of my thoughts and suggestions. You really have a lot of possibilities for what you could do with this. Hope these ideas helped. I'm sure whatever you decide to do with this story will turn out great.

In Christ,
Jordan aka Mr Squishy

Sounds good.