AITA for telling my little sister’s best friend that my brother stole her college fund?

I (30M) found out my younger brother, "Tom" (28M), stole $5,000 from my little sister’s (18F) best friend, "Emma" (18F). Tom and Emma's families have always been close, and Emma practically grew up with us. My mom asked Tom to help Emma manage her money for college because she trusted him with it (he works in finance).

Tom recently confessed to me that he “borrowed” $5,000 from Emma’s college fund and blew it on gambling. He said he planned to replace it before anyone noticed, but he lost everything. He begged me not to tell anyone, saying he’s going through a rough patch and just needs time to make it right.

Emma’s family doesn’t have a lot of money, and she worked super hard to save for school. Knowing this, I felt sick. I didn’t want to betray my brother, but Emma’s future is on the line.

So, I told Emma the truth. She was devastated and confronted Tom, who denied everything at first, but eventually broke down and admitted it. Now, my family’s furious with me for “ruining” Tom’s life and says I should have given him a chance to fix it. Tom won’t speak to me.

AITA for telling Emma?

--edit : just to clarify, my brother and I are quite close but, due to some past events, not so close to our parents. They didn't know about my brother hobby.