For a minor character, Embry had a lot of potential. There were three potential candidates for his father, one of them being Billy Black. This means that he could be Jacob's brother. But since this would have taken facetime away from Edward, SMeyer never developed this. When asked about this, she said she didn't know who Embry's father was, complete with that she didn't know until the end that Rosalie hated Bella. OMG woman, the readers figured that out before you did! But hey, what would you expect from the great SMeyer?