Can older brother claim HOH, CTC & EIC for younger brother while non-custodial pays over half the child's support & court forced custodial parent to sign form 8832?

What happens when a non custodial parent pays child support and a non parent claims the child because the child lives with them?

Custodial parent is disabled, married, & lives with their spouse & with my two sons ages 20 & 15. My older son is the only one that works & allegedly pays all the bills. Older son claimed HOH, his parent as dependent, & his younger brother. I went to court to enforce the form 8832 & custodial parent was forced to sign it for me per the court order , and I plan on filing a tax return and claim the CTC for my younger son. I understand the IRS doesn't care about court orders & fear that my son will move ahead with his current filing status. I will be able to prove to the IRS that I pay over 1/2 of my youngest son's support, but, I believe what I pay in support is more than just the support of one person; there is enough left over to cover another household member's support. They live is a subsidized household & expenses are very small. Will my son be audited? If so, If I can prove I provide over half my younger's son support & then some, would that then not make him eligible to claim HOH & EIC? I'm am very worried about this. 

(HOH - Head of household EIC: Earned income credit CTC: Child tax credit). Thank you!