Hi,
AFAIK there is no way to do this. You can only switch on/off collision (if there is no fancy new plugin I don't know).
Maybe you can create a workaround like switching off collision for one of the two persons.
Or switching off collision for an object, but add an additional invisible object to the part where one of the person will be touching it, but the other one doesn't.
Hope this may help a bit.