So in your "family scenario" where do SISU fit in?
As a suggestion - SISU knock on the door of the "desperate parents'" house and tell them that they need to come in so as to give them glad tidings (well, you did say it was Xmas) of their wonderful lottery win. However, once through the door the evil SISU looks around for something of value that can be "liberated" from the house. Finding nothing, SISU then stumbles and knocks over the Xmas tree setting in chain a series of events that ends with the house being burned to the ground.
How's that sound?