Left out of the family trust, would I be wrong to ask the others to split the money?

I know this sounds entitled as hell, but please don't judge until you read the whole thing.

My mom died at the beginning of the year. She left all her assets in a trust to be split between her children and grandchildren. At least that is what I was told. Everything is still up in the air about when the money will be divided; the brokerage account has totally jacked up the paperwork.

I finally asked my sister, who is in charge of the trust, for an update, only to find out that my son and I were not part of the trust because my mom had given me a significant cash gift almost 20 years earlier. This "gift" was for my son because he has special needs. The money went into a special needs trust that can only be touched for his expenses after my death.

I know that I do not have the right to tell my mother what to do with her assets, but why the hell am I always left out of things? My sister told me that my mom said I knew I was not getting anything when she died.

The grandchildren and my siblings will each receive the same amount my son was gifted, while I receive nothing.

At first, it did not bother me, but the more I think about it, the more upset I am getting. Honestly, I have always been on the outside looking in when it comes to my family, and now I feel like I am getting screwed.

Part of me wants to ask the others if they would be willing to give me a small part of what they are each getting to make up for being left out.

Mostly, I am just venting here because I needed to get this out.

I honestly want to know, do you think I would be wrong if I asked the rest of the family to gift me part of their money so it gets divided evenly?