I too agree with what Eric said above
Just to give you an idea for the "star-crossed lovers" scenario, my own primary character (alas, probably never to be played again. . . ::weep::) is the son of a val'Virdan and val'Emman: two families that even today hold great hatred for one another. His father is a val'Virdan Coryani patrician from a branch of the family who avoided deportation to Canceri in the 4th Century I.C. by converting to Illiir, and his mother is the daughter of first generation Coryani from Cancerese refugees who were chased out of Canceri for their (unknown to them) val'Emman heritage. When Nierite worship was allowed again in the Coryani Empire some 50 years ago (after some 700 years of being outlawed), both branches openly became worshipers of Nier in the Empire, and the two met in basically "Nierite Bible School". Much to the shame of both sides, they forged a relationship and raised my character (and his two siblings) well away from the heart of the Empire in the then-newly formed Province of Nova Cormata. They have since risen more to prominence, but are still considered outsiders to their own families to a great extent because of it.
These backstories add substantial colour to a character, and define their motivations. In your case, the human child of a Khitani and a val'Abebi would be outsiders in both sides of their heritage because of the choices of their parents. The Khitani wouldn't accept them as one of their own (outside of the First City, and even then it is questionable), and the val'Abebi wouldn't recognize the kid as one of theirs (since they are not a Val, their is little the val'Abebi can do to acknowledge the child). This mixture is entirely valid, but it should inform your characters motivation. They should have a personality that reflects their in-betweener, but not belonging status. Maybe they became a loner? Maybe they are overcompensating by championing one side over the other? Maybe they seek solice in a group like the Legions or the Shining Patrol?
As another example, my wife's secondary is a gnome: born of a Saluwe' worshiping human and a (Tir Betoqi?) dwarf. In her story, the gnome's parents loved each other and him very much, and raised him as best as they could. However, society intervened, and his parents were killed for the abomination that they brought forth and their forbidden love, causing the gnome to have to grow up on the streets. However, while my wife plays the gnome as mournful, she plays him as almost painfully pure and innocent, almost always seeking the best in people because he knew true love in his life from his parents, and he knows that despite his flaws, he has value and so do everyone else.
I guess what I'm trying to say is that, while these character concepts are great, they should INFORM your character and not define them. It is a great building block, but it should only be part 1 in the process.