I have older brother & sister, and I'm age 65. Our relationship has not been that great over the years. Mother maybe a factor. I read 30% of siblings have problems for very many different reasons. It also said many times it all has to do with the younger years, and one child can have ideas why another is different. Like treated better, and such. In some cases, parents can better provide for the older children due to better income. But the list goes on and on if you search Google - sibling rivalry. There is just no way to know how it could have been.