My brother(45M) cut ties with my parents(75M, 70F) and my family, everyone but me, and I don't know what to do. How can I convey the situation to my mom?

TL;DR: My brother had enough of my mother favouratism to another brother, and decided to cut contact. Yet my mother refuses to accept the situation. Help/

I come from a middle Eastern country. So sorry for bad English. also sorry for long post

My parents have 3 sons and one daughter. While I am the youngest (32M).

My eldest brother (John 50M) is BY FAR the favourite child by my mother. My father doesn't express opinions often. When John was born, he had many health problems, so my mom practically lived with him in the hospital for the first year.

Every time we talk about something, the topic changes to John- I can tell them that I have problems at work "Oh, John just solved his problems with his boss. Take an advice from him" when talking to him - nothing of the sort happened. My mom expeditated a meeting he had with his boss. It might be in my head but I even have the feeling that she sometimes addresses my Gf Joanna as Johna.

John can treat out parents however he wants - yet they magically forget it after 2 days. When I was in collage, my mom called me crying, with enough urgency to ask me to leave class to take her call. apparently, John was very mean to her. The day after - my mom gaslit me saying it was nothing. Needless to say- there is never an apology from John.

Except for my sister (Mary, 40F) who holds a government position, and my parents who are too old. All the siblings moved to different countries. John to Europe, James to Canada, and me to Australia.

My parents visit John in Europe about 3 times a year, for 2-3 weeks a time at his country. They spend more time with Johns family than with my sister's. They visited me or the 2nd eldest James once. (James moved to Canada about 6 years ago).

My mother had a lot of problems with James and Mary. Ended up in couples therapy with both. Both times my mom claimed that their respective spouse is "Taking her child away from her" and "whispering mean things to them about her". Etc. etc. While Mary had more emotional problems (Mom doesn’t love her as much as John. Mom doesn’t care about her children. Mom keeps on alienating her spouse) James’s problems were very monetary. He claimed that the parents gave him less money than to James. As well as babysit his kids less.

As the last one to leave the nest, I had some more knowledge about my parents’ finances. And I can say that except for one incident, which I will address later, my parents gave about 250K dollars to John, about 300K to James. About 100K to Mary. And about 50K for me (I went back to grad school and did not get married yet, so I did not need much).

In about 2010, my parents received a plot of land near their house. And told all the children that if they wish to have it, they can - if they agree to the following rules:

A. The building of the plot will be led and mainly financed by the child.

B. The child will live in said plot and help take care of the parents, who are growing old and in increasing need of aid.

Mary who held a government position on the other side of the country, and me who only finished high school were out of the picture.

And James and John could not decide.

James insisted that due to the high value of the land it needs to be sold and split between the siblings. While my parents said that its a no go.

After 2 years of debating, John picked up the glove and build the house. Later living in it for about 4 years. Before leaving the country due to work relocation (not by choice. But this is another story.)

James felt, and still feel robbed.

The main incident happened half a year ago. My parents, who are still in need of aid, decided to buy a house in Europe, next to John. Claiming "this is an investment for the future, when we will pass on, this house will be passed to you OP"... While I live and plan on settling in Australia, which is, in fact, very far from Europe...

When James heard about it, he blocked my parents. And a month ago, after he calmed down, he told me that he decided to cut ties with my parents. That he felt 2nd best at most, that he couldn’t shake the feeling that this animosity towards his wife continued for so long, and he is afraid to have the same treatment to his kids. He is also in therapy.

My mother on the other hand is crying non-stop. About reaching out to him, about trying to go back in touch, about seeing her grandkids. She asks about him every day, and I don't know how to break it to her.

The worst thing - she does not accept blame or guilt. She constantly gaslight things about everything being his fault etc. and now I'm stuck in the middle of this charade. And she acts as if “trying to change her in her old age” is some sort of a crime.

How can I tell her “Look, his life are better now without you. It is your fault and he cut you off knowingly. If you ever will be given a second chance you will need to earn it."?

How can I convey the situation to my mom? Do you have any advice regarding solving this? Thank you in advance.