The article below describes how this can happen, mostly focused on several factors. One, things change. The family’s circumstances change over the years, your parents change over the years, and so an older or younger sibling might have been raised differently than we were. Also, we are different. Some kids’ personalities mesh differently with their parents compared to their siblings. That’s all pretty normal. 

I want to talk about childhood abuse, especially why it can seem like our siblings don’t understand when we tell them about our abuse. One of the things that becomes clear as you read the link is that kids might grow up in the same biological family but not necessarily in the same circumstances.