I don't know anything about being a teenage boy who has lost their father, but I know an awful lot about being a teenage girl who lost their mom; and I remember how more than anything I hated it when people would say to me, "I know how you feel, I lost my...(fill in the blank with someone other than mother)" I remember how I hated feeling different, (what teenager wants to feel different?), and I remember how I just desperately wanted to be heard; so the best advice that I can give to you is to remain open and honest, be sympathetic, but don't offer pity, don't treat him with kid gloves, try to keep things as normal as possible, and be available to listen when and if he wants to talk. Reassure him, that in time it will get better, but be realistic, this isn't something that he is going to get over, losing a parent is life changing, and now his life is forever changed. In time the sting will lessen, but he will have moments, some big and some small that will bring it all back. Encourage him to find a positive outlet, (mine was writing), and allow him to go through the stages of grief at his own pace. Try not to worry too much. It isn't much as far as advice goes, but I do hope that it helps.