Sons were named as beneficiaries when they were minors in their uncle's trust. My ex brother in law , who passed away,and my ex sis in law

Is the trustee. My sons are now 18 and 19 and have college expenses including loans. My sons do not nor did they ever have a true relationship w/ their "aunt" and their father has been estranged since 2007. Prior to my brother in law passing he telephoned informing me he was naming the boys in his will and the inheritance could be used for any school tuition. They have been in parochial school since kindergarten and it was court ordered their father did not have to contribute to their elementary or high school tuition nor does he. My eldest is at the univ of San Francisco and my 18 yr is considering Gonzaga . Even with scholarships , loans and work study we still come up short. Long story short, their estranged aunt has made it clear that she intends to keep their inheritance in a custodial acct until age 25. she also says in a letter it was Bob's intentions to help offset the cost of college. Well they are 19 and 18 and are incurring debt/college exp. How do they petition $