Why don't you take matters into your own hands and become close with the dog? Because once you loose someone, I think it's always nice to bring something else into your life, not to replace, just to help. Practice trust with the dog. Then spend time with the dog. Encourage him to eat. If your worried about if the dog will forget about your brother and go for you, the chances are low. Once dogs form a bond with someone, that relatioship is priceless, unbreakable, and can't be replaced.