Is child support being abused?

My mother and father have been seperated for about 6 years, I am 24 years old, I have a 18 year old sister who is in college and a 16 year old brother who both receive child support from our father. The checks are made out to our mother as both children are under age.

The issue with this is neither one of the kids live with her, she does not provide any form of support for either one of them and she's cashed the checks and has not given the full amount to the kids.

I have supported my sister financially and had her living with me while she was in high school, I opened a bank account for her and I am willing to open a seperate account for my brother to ensure that they are receiving the money they are entitled to. Is there anyway to have the checks deposited into their accounts?