In India, every house has something called Kula Devata or Family Deity. What is the historical reason for having such Family deity, and on what basis are family deities assigned to families? Is there any historical, ancestral or political connection between the Deity and the family that worships it? Does it have any relation to the region in which the Deity resides? As I see, there is no strict caste specific restriction on having a particular Deity as your Kula Devata. Can anyone here shed light on this, or mention similar practices being followed elsewhere in the world/other religions?