Ron had been torn between going to Corner's party or heading to Al's. On the one hand he was fond of his nephew, and not just because of the family thing, and still thought of Corner as a right git, but on the other he knew Harry would be with the "grown ups". That is, if he was in a party-going mood, which probably would not be the case given that he had just arrived. In the end, though, the possibility of Harry being there won. Well, that and the idea of alcohol being served.
He was enjoying his first drink (and looking around in search of Hermione, getting ready to meet a disapproving stare) when he heard an unfamiliar voice talking to him.
"Yeah, I suppose you don't," he said, absentmindedly.