[hopefully not ending in Gawain and Mordred punching each other.]
Gawain raises an eyebrow. "What, can't I say hello to my big brother?" "Gawain!" Gareth hisses in his ear. "Stop being an ass."
He turns to the other two, with a look that practically reads: 'please excuse my brother, he hasn't taken his sane medication today.'
"I apologise," he began. "It was kind of my fault, because I saw you and..." he trailed off, as he noticed the man hiding behind Mordred. I mean, really noticed him.
"...Gaheris?" He took a cautious step closer. "My God, is that you?"
Still asking ridiculously obvious questions - that's our Gareth.