What I like most about Motya is that he doesn't even know he is half Omestri. He has grown thinking he was a Varyan whose family had been sentenced to slavery, the only people that know of his Omestri blood would be Mother Oksana (if she put two and two together when she liberated hum from the mines) and the Inner Circle. I like knowing that it can become something that he has to deal with as a character. He already has an affinity to freeing slaves and liberating the commoner and detesting slavery so how much further could that go if he were to find out about the Omestri half.

It is likely Motya would Identify with your character Arch because of the common slavery background but it might be an odd relationship because unlikely your character Motya is outright gregarious, boisterous, and extroverted.