I'm not sure that Marvin really knew who they were. He's a rather friendly cat (being huge and bitey does allow a cat to feel unthreatened) so he could have just been being friendly to the random humans.

Mind you he did let Jack pick him up and tickle him in ways I've never been able to... Without losing a pint of blood :-)

It's kinda weird that the two cats, formerly companions, are on opposite sides of the planet...