Therapy question

My threapist used a term today that I am not familiar with. He used a term called "Shared Sheilding". It is a newer concept and he seemed very excited to learn that I experienced it. The concept involves siblings who are very close where one sibling will take the brunt of a traumatic experience for each other. In these cases it is common for one of the siblings to not have any recollection of a shared truamatic experience while the other remembered every detail of it and vice versa. If you have any more knowledge about this concept please let me know. I am not able to find any readings on this subject.