how to protect family from father’s lack of financial self-control?

mother passed away recently, did not do estate planning, so all savings automatically went to father. mother was single-handedly controlling finances because father lacks self-control.

siblings and i are still students. have a special needs sister who will be taken care of by us for the rest of her life as well, which is why i’m so worried about our finances.

father earns 10k a month, but none of this goes into his savings or the joint account. my mother has been the only one contributing to the joint account and paying for siblings and i’s expenses. father has a gambling addiction. used to go to the casino all the time, drained joint account, which was why mother changed the pin on the joint account and he lost access to it (but apparently he never added any money to it anyway, so no loss there). his gambling now consists of “investing” — he buys crypto and stocks, but when you spend your whole paycheck on that, it’s no longer investing, it’s just pseudo-gambling. he also spends quite a bit on online shopping and maintaining his aquariums.

he has less than 20k worth of savings. scary since 20k is just two months of his salary.

i recall when a family friend asked him what he would do, hypothetically, if he won the lottery, and he explained the kinds of mega shopping sprees he would go on, before my family friend interrupted in horror and asked why he didn’t think of saving any of it for me and siblings, especially special needs sister. this is a man who clearly only thinks for himself.

he insulted this family friend to the point where they cut us off, which is why i’m afraid of confronting father about his issues, he could do much worse to me and siblings. i’m not confident that mother’s death has changed his ways and made him a more responsible man.

this is a man who spends 10k a month without even thinking. mother’s joint account and savings are sizeable (at least 250k). even though it’s a lot, i don’t know how much father’s expenses will balloon after seeing this amount. will he go crazy spending it all away over a period of a few short months? i suspect so.

i’m really scared and i want to find a way to protect siblings and i. especially my special needs sister, that money could go a long way paying for her school fees, possible speech therapy, future adult care. but i’m not sure if there’s anything i can do. any advice? or is father automatically entitled to spend the money however he wants?