My brothers won't help out with my dads gift?

My dads birthday is in a couple of days, but we have to get it tonight because we're going to his house tomorrow. Well, neither of them will help out at all with it. They don't pitch in any money, help with any ideas, go to get it or even simply make a card. Which mean I get stuck with all of it. They do this every year for all of our relatives birthdays and then they tell me to stop being selfish and let them sign the card like it was from them too. I'm 15 andy brothers are 16 and 10. I understand the 10 year old can't make money, but he knows perfectly well how to make a card on the computer. Is this fair? And is it actually selfish to not let them sign the card when I'm paying for it, picking it out and wrapping it?