Short answers, pulled from the story.
Around 30,000 years ago, the number of modern humans who lived to grandparent age increased significantly. The exact cause is unknown, but a key consequence was that three generations could be alive at once, allowing knowledge such as where to find water during drought to be preserved and passed down.
According to a 2012 study based on 2010 census and survey data, around 10% of children in the United States live in a household that includes a grandparent. Of those, approximately a third live with both parents and a grandparent present.
Singapore established the grandparent caregiver tax relief in 2004. It allows working parents who are Singapore citizens, with children aged 12 and below cared for by unemployed grandparents, to receive an income tax relief of 3,000 Singaporean dollars.
Swedish has no single word for grandmother: a mother's mother is mormor and a father's mother is farmor. In Bangladesh and Pakistan, maternal grandparents are Nana and Nani, paternal grandparents are Dada and Dadi. In the Philippines the terms are lolo and lola; in Friesland, pake and beppe.
US research finds that grandparents involved in childcare are more likely to suffer heart disease, hypertension, and body pain compared with non-caregiving grandparents. However, grandparents who provide long-hours care are also more likely to maintain better cognitive function and are less likely to develop dementia.
A Court of Cassation ruling on the 8th of July 1857 first recognized the right of grandparents in France to visit their grandchildren. That right was not enshrined in statute until the law of the 4th of January 1970, as part of a general overhaul of French family legislation.