BIL has twins, I was only able to have one child. So I felt like I was being punished for only having one. Every Christmas, birthday, etc they always got double. Then she decided to give each grandchild $ 1000. DH actually argued with her over it, and we gave her back the $ 1000 on principle. Stupid but that's what we felt.
My DM always gave Christmas money to each person. I always felt that was wrong because one DSis was unable to have children. When my mother because incompetent and I took over as POA, I gave equally to all 3 of us, also because I felt the other way I would be getting more than them.