Sirius made a bit of a face. Had he known or thought Regulus were going to react like that, he may have changed his answer. Honestly, he had enough going on in the country to keep him occupied, but it wasn't something he could just share with Regulus. And that...he almost sighed, licking at his ice cream so as not to start making a go at his brother.
"Look, I'd not be careful about it," Sirius replied, "but you can go about it the right way. I can find out more about him. And he could meet mum and dad. You can bet they won't let you go if he's a tosser." He knew that much at least. And sure it was possible to hide it, but if nothing else, their mum had always been good at applying uncomfortable pressure.
"Just be smart about it," Sirius grinned, "unlike me."