Jacques is a wealthy older American businessman, born in Belgium, who enjoys entertaining younger men. He is the one who takes David to Guillaume's bar, and initially it is Jacques, not David, who is interested in the new bartender, Giovanni.
When they all go to Les Halles, Jacques gives David advice on his relationship with Giovanni. He says, "Love him. Love him and let him love you. Do you think anything else under heaven really matters?" (1.3.98). It is clear that Jacques projects his own desires onto David, but he also observes that David is ashamed of being gay and takes pride in helping him overcome his feelings of shame.
Jacques is a morally ambiguous character, as pitiful as Guillaume but not as mean-spirited. He gives David and Giovanni money when they are in the depths of poverty; he helps Giovanni find David after David leaves without telling him; and he takes Giovanni in after David breaks with him. Like Guillaume, he lives vicariously through the young men, but he is more open about it and is never forceful with either of them.
At the start of the story, David casts Jacques in a particularly harsh light, noting in particular that he did not give Giovanni money the last time that he came to him for it. As the story goes on, however, it is clear that David is far more in the wrong than Jacques, and that part of his grudge is based on the fact that it was Jacques who forced him to admit the truth about his sexuality.