I'm so sorry, Chick Lovers. My 16 chicks are exactly 15 weeks old too and of them, 3 are barred rock pullets and one is a barred rock cockeral (a young rooster). My barred rock cockeral looks exactly like yours. My 3 barred rock pullets look very different from him, hardly any comb and much smaller. Also, when the barred rocks stand side by side, I can definitely see that the the pullets are more darker than lighter in their barring and the cockeral is more white than dark in the barring. I can only see this difference when they're side by side though, otherwise, it's too subtle for me to pick up on.
Does your father have to kill him because you can't keep a rooster? If yes and it helps... of my 16 chicks, 8 are cockerals. In such a small flock, with only 8 hens, I can't (obviously) keep 8 roosters. So, I need to cull 6 of the 8 roosters. My barred rock will be my main rooster because I like him best and he's nice to the others but is the boss. A good boss. Plus, I'm keeping a second rooster as a spare in case anything happens to the first one. So... I have to cull 6 roosters. I'm going to honor them, however by making them for my family's dinner table. I've never done this before and I'm not at all looking forward to it (ok, I'm dreading it) but it's the right thing to do. My husband eats chicken from the grocery store and I know how those chickens are treated. Mine have had a very nice life but this is the way of the farm. I could try rehoming the roosters but the truth is, there are already so many roosters in this part of rural Kentucky. It's pretty strong odds that they'd end up on someone else's dinner table regardless.
If your rooster must be killed, could you let his life and his death have meaning and value...? "The Small-Scale Poultry Flock" has some great step by step pictures for how to prepare chickens for the table and how to do it humanely and well. Also on page 280 is a really good writing that is kind and understanding about how butchering chickens for food can be viewed as not harsh or as difficult, but as an integral part of the chicken keeping.
Good luck to you and your chickens,
Guppy