Grandparent

Grandparents, individually known as grandmother and grandfather, are the parents of a person's father or mother – paternal or maternal. Every sexually reproducing living organism who is not a genetic chimera has a maximum of four genetic grandparents, eight genetic great-grandparents, sixteen genetic great-great-grandparents, thirty-two genetic great-great-great-grandparents, sixty-four genetic great-great-great-great grandparents, etc. In the history of modern humanity, around 30,000 years ago, the number of modern humans who lived to be a grandparent increased.^{[citation needed]} It is not known for certain what spurred this increase in longevity,^[1] but it is generally believed that a key consequence of three generations being alive together was the preservation of information which could otherwise have been lost; an example of this important information might have been where to find water in times of drought.^[2][3]

In cases where parents are unwilling or unable to provide adequate care for their children (e.g., financial obstacles, marriage problems, illness or death^[4]), grandparents often take on the role of primary caregivers. Even when this is not the case, and particularly in traditional cultures, grandparents often have a direct and clear role in relation to the raising, care and nurture of children. Grandparents are second-degree relatives to their grandchildren and share 25% genetic overlap.

A step-grandparent can be the step-parent of the parent or the step-parent's parent or the step-parent's step-parent (though technically this might be called a step-step-grandparent). The various words for grandparents at times may also be used to refer to any elderly person, especially the terms gramps, granny, grandfather, granddad, grandmother, nan, maw-maw, paw-paw (and others which families make up themselves).