First, we printed out a few photos of couples in our family - my kids' parents, grandparents, and great-grandparents - and we laid them out on the floor. I talked with my kids about how long each couple has been married and explained that an anniversary is what we celebrate each year to remember their wedding. We rounded to the nearest ten; for example, my parents have been married 41 years, so we rounded down to 40. Then, using one block to represent ten years, we counted out the length of marriage for each couple by tens.
Extension: For older children, go back further in your family's history. Using obituaries, death certificates, or other records, find out the life spans of earlier generations in your family tree. Graph out those ages, too, and try to look for patterns in longevity or recurring hereditary health problems.
©2014, copyright Emily Kowalski Schroeder.