Question about the groom at the 'end' (spoilers)

So at the end of the film we see that the time traveller chooses to stay beyond his 11 minute window and get stuck their forever. The groom follows him out of the room and says to him, "You're not supposed to be here." The camera starts fast forwarding and we see that the groom talks to him for a couple minutes, but we don't know what about. We see the groom come talk to him a couple more times during the 2 hours, again we don't know about what. It seems likely that the presence of this guy is what is disturbing the groom and that's why he drinks so much.

My question is, does the groom somehow know who he really is? The "you're not supposed to he here" could be interpreted as simply "you're a wedding crasher", but then why would the groom leave him alone, get upset by the guy being there, yet not throw him out?

It felt like we were intended to interpret it as the groom knows that the man is a time traveller, but how would he know that?


"My name is Paikea Apirana, and I come from a long line of chiefs stretching all the way back to the Whale Rider."