I usually have an heir for each household who stays at home and raises their family with the grandparents. If there are additional children, they usually move out and form new households for my rotation. Sometimes their in-laws live with them, but usually when my sims marry pre-made sims who have parents I age up the parents to elder at the appropriate time and move them into my retirement village household.
I play with aging off except for the active household so no one ages unless they are in my rotation of played households or I go in and age them with birthday cake. When I play my retirement village they do a lot of holidays and outings with their children and grandchildren, as well as vacations and club meetings together.
