@Zippy27
For instance your wedding money is worth £7,700 today, 5 years childcare for 2 children 1 day per week is £26,000.
If for example he has been given double the amount of deposit because he has no partner (and never will have to pay half the bills)… comparably there isn’t an enormous amount of difference between the £45k and £34k you’ve had.
Looking at it, he has major mental health, probably autistic by the sounds of it, and him being displaced from his home could really destabilise him.
So your parents have stepped in to help prevent this and have given inheritance early.
You meanwhile, do not have major health problems causing disablement, you have a husband to support you emotionally, and financially to pay half the bills.
I think you need to think of this with your adult, rational brain rather than having an emotional response linked to childhood resentment of your brother, no doubt fuelled by your being an only child and the centre of attention for 12 years.
I say again, you are only hurting yourself and your family with this behaviour and potentially cutting your children out of a few hundred thousand in the years to come when your parents pass (taking into account their home and savings).
I would suck it up, talk to your parents like an adult and try to come to some sort of compromise.
Family is worth more than money, it isn’t worth embittering yourself.