Sirius wanted to believe James. He wanted more than anything for him and Regulus to be okay. He'd never really given up on him, and now that he was back there was actually a chance. But nothing was ever simple with his family, and Sirius knew if he opened his heart again he was just setting himself up to get it broken again.
"Right, my piglet! We named him Hamlet. Bollocks, I'm going to have to see Snape all the time now, aren't I?"