If there is any advice you can give me on how to approach this matter please help.
You guarantee your sister, at the police station, what are you doing to provide opportunities for your sister to bet/debt again in the future.
Question:
1. How many times has your brother been in trouble with the police, 1,2,3.
2. What case did your brother get caught, gambled or owed.
Now there are two problems that have happened to your younger brother, gambling and debt.
1. Gambling addiction:
Solution:1
You can put your brother into gambling rehabilitation, don't let him hang around and be friends with his gambling friends again, it could be even worse, because you have guaranteed it, he thinks later if I get caught again and get caught, I will guarantee it again brother.
Solution:2
If your younger sibling doesn't want to go to rehab, don't guarantee it anymore, if he gets caught again in the future, let him go to jail, make him a deterrent.
2. Debts:
Solution:1
Here it is clear your brother, owes money to gamble, if she wants to change and wants to be rehabilitated, pay her debts, but if she doesn't listen to your suggestions and advice, let her debt be borne and don't bail her out at the police station.