James Wilson is a doctor, specifically an oncologist (cancer specialist), that sometimes works with Gregory House. He is Princeton-Plainsboro's Head of Oncology. Dr. Wilson is also Dr. House's sole good friend. In Season 4, he started dating Amber Volakis, and it was revealed in Don't Ever Change that they had been dating for four weeks, since she was fired.
As befits a doctor whose practice consists primarily of patients who are terminally ill, Dr. Wilson is sympathetic, thoughtful and compassionate. However, there are clues his personality is far more complicated, and that he essentially buries his darker side within himself. He has been married and divorced three times (first wife's name is unknown, the second wife was Bonnie, the third Julie), and cheated on all his wives. He has had an affair with one of his terminally ill patients. He is currently being treated for clinical depression. Although he cares deeply for House, he often goes behind his back in attempts to help him. For example, although Cuddy proposed the bet to House that he give up Vicodin for a week in order to reduce his clinic duty, it was Wilson's idea.
House with Wilson
Although House is often abusive to Wilson, Wilson is perfectly capable of giving as good as he gets. In one instance, he learned that House was deliberately borrowing money from him just to find out how far Wilson would take it. Wilson retaliated by lying to House, to see how far he could go before House realized the truth. On another occasion, to retaliate for House eating Wilson's bag lunch every day, Wilson sawed partway through House's cane so that it broke when House put his full weight on it.
Wilson's heritage is at least partly Jewish. Since Wilson is not a common Jewish name, he may be of mixed background.