10/31/2011 03:44 pm ET Updated Dec 06, 2017

Calvin Klein & Nick Gruber Dress Up For Halloween (PHOTOS)

In case the fact that Calvin Klein is dating someone young enough to be his son (or even grandson) slipped your mind, the pair's latest outing over the weekend should certainly jog your memory.

Calvin Klein and his male model beau Nick Gruber made a rare joint appearance this Sunday, attending the Saints and Sinners Halloween bash at The Standard in NYC.

The two are hardly photographed in public together, possibly due to their on-again, off-again relationship status. But let's not forget about the extreme age difference... Nick Gruber is only 21 years old, while the legendary designer is 67. Age is just a number, right?

Other than a classic May-December couple, we weren't quite sure what CK and his shirtless boyfriend were dressed up as for the fete. But Klein filled in on their intended characters: "Sinners, of course!"

Only if the sin is gossip... this relationship is one that always gets people talking.

Check out some of the other rare sightings we have of Calvin and his younger half from the past year.

Calvin Klein and his model bf