I'll rant on this one. I have two colleagues in a relationship in my office, the *worst* distraction ever is having them sit across of me constantly chuckling, bickering and poking each other while doing *no work at all*. I fucking hate this shit, drives me nuts -_-

It will be worst if they are in the same team as you and the workload increase...

Can't tell you what to do, but if it were me I'd become the commandant of awkwardness by joining in the fun, or just standing way too close, like a third wheel that just won't go away.

Or every time they started up I'd tell them, loudly, to "make sure you use a condom this time!"

If they're gonna annoy you, why not have some fun at their expense?