How about this: Doyle's younger brother on his mother's side. Completely human, yet an ex-soldier, (but way better than Riley. Let's face it, he wasn't that good of a soldier). I'm very hard assed, trained in special ops, heavy artillery and many lethal forms of hand to hand combat. I, in fact, give Angel a run for his money. Seeking vengence against Angel for my brother's death, not knowing the real story of what happened. When the truth finally comes out, after a knock down, drag out fight with Angel, I join in the fight against evil. As they get to know my character, little bits and pieces come out about Doyle's death and how a woman and a demon had a child, which explains the hatred for demons. He mellows out a bit as time goes on, knowing that not all demons are mean and evil. As he and Angel trust each other more, Angel tells him stories of Cordelia and through stories and pictures, he falls in love. However, knowing it will never come to pass, he looks for other forms of... love. However, a big bad, unnamed right now, figures out this infatuation he has with Cordy and produces a replica of her and they continue to meet in secret. The big bad's intentions are to bring down Angel Investigations once and for all and bring Angel to his knees. After all is said and done, this character is cast off, despite being Doyle's only living relative and he travels abroad. Using the knowledge that he obtained while working with Angel, he finds Buffy and the scoobies and slowly gains their trust and becomes a part of the team...
Just off the top of my head. I'm sure if I sat down and thought about it, the story would be more interesting.
