The happy-ending stories that Marsden has observed mostly occurred in a clinical setting. The rapprochement usually starts out small, maybe with a text message here or there or small talk at a family event. One dynamic he sees often is that a controlling parent - or both parents - turned one sibling against the other long ago. If the parent alienator is incapacitated or dies, the sibling who was aligning with the parent can start to feel differently. "You start to question your own beliefs, and you might slowly start to reintegrate," Marsden said.

'It's an experience that a lot of caregivers have, where it tends to fall on one sibling's shoulders.' Kim Elliott, founder, Gray Monster

Bill Eddy, a longtime conflict resolution specialist, also describes relationship dynamics between siblings that can be similar to a divorcing couple trying to make it work for the kids. He points to the fact that people are generally stuck with their siblings and can't legally cut them out of their parents' lives or their own. They just have to try to make the best of it, he said.

While most of Eddy's work is focused on acrimonious couples, he is getting an increasing number of requests to apply the principles of high-conflict divorce to families dealing with eldercare. Usually, the one reaching out for help is the sibling tasked with holding power of attorney or serving as executor of an estate, and who is being hectored by a troublesome sibling.