Harville is one of Captain Wentworth’s closest friends, and the one who brings Wentworth (and eventually the whole Musgrove clan) to Lyme Regis. Harville slightly resembles Mrs. Smith – he’s in poor health due to an injury, and he’s not the richest guy on the block. Like Mrs. Smith, he makes the best of his situation through the "usefulness and ingenuity" (11.18) of his mind, but unlike her, he’s got a family, and his friends Wentworth and Captain Benwick, to provide moral support.
When the Harvilles invite the Musgroves for dinner without concern for how their small rooms might not fit everyone, they show how different they are from the Elliots, who choose not to invite the Musgroves for dinner in Bath because they don’t have the stuff to be as showy as they would like. He and his wife take in Louisa after her accident and take care of her for weeks, no questions asked. Harville’s hospitality and kindness despite his limitations make him a poster child for the British Navy, and for good friendship.