I happens a lot in israel, i heard of a bunch of such stories and i know some of them- i have two friends that their grandparents remarried,
i think people keep it a secret usually because it’s a later age and they don’t need the publicity.
CTLAWYER- i don’t think the money is most people’s reason for not remarrying as their happiness is more important for them and for their children who want their parents to be happy,
also the reason many people don’t remarry is because second marriage especially in old age is difficult, many people are afraid of the change and many people have a hard time finding the right zivug they want to spend the rest of their livers with, and/or are afraid of being widowed too fast once again.