HOW TO CORNER A TRUSTEE

There`s a trust which was formed when an amount was awarded as
compensation for my father`s death. It was formed because my brothers were
minors at that time.Therefore the amount was held in a US` bank in a trust
with four trustees.One of them is my uncle.
The condition was that as the beneficiaries turn 18 they can take the money.
Now when they are 18 and want the money,the trustees are not co operating
with us to take the money.
Is it possible to take the amount without their involvement