Here is another thought:
What about that time that Christian and Claire were in the cabin? Can MIB (man in black) be two people at once? Is Claire even really dead for him to take her form? She could just be brainwashed to follow him since Christian is her dad, she may just be doing anything he says, trusting that he is right.
Also, an "Anubis" Egyptian god of the underworld (which is what the statue is of), so if MIB is an Anubis, then it would make since that he could take the forms of dead people.