By Rachelkat:

Macavity is this cat who thinks he's all bad because he shows up and 
dances and gets his henchrat to throw nets on people's heads. I think 
he's doing something to get revenge on Deuteronomy. Maybe Old D threw 
him out, and so he's come back to avenge the loss.

Mac does it all. Killer, thief, lover, dancer, evil laugher, 
levitator, all this and more. Who wouldn't want him for a mate, eh? 
Well apparently none of the older female Jellicles, who all seem to 
have unresolved issues with Macavity, even Jellylorum and 
Jennyanydots, who swipe at him a bit right before he puts the lights 
out. Maybe for a future mate, however, he might try to turn one or 
more of the kittens on his side. I think he would try to get Demeter, 
too, but she's already been traumatized enough by the guy, so she 
probably won't go with him. The only people I can think of who would 
go now would be Bomby the flirtatious, except she's too attached to 
Demi, and Jemima and Victoria, the two most trusting kittens, who 
might not realize what he wanted.

I can't even guess as to parents, since he's so freaky looking, but 
assuming Bombalurina hasn't been his mate ever, she might be his 
sister, since they are both red. Macavity's probably the father of 
someone like Electra, who has a bit of red in her costume.

Overall, the message Macavity wants to give out is that he's bad, and 
not to mess with him. But we know he's a big softy, or else he 
wouldn't be pining over/kidnapping Demeter like he is. -_^