Greetings.   Will try to keep this short.
My wife runs a pre-school in our home.   One of the dads is a army vet with a disability, from what we have been told.  He is divorced from his wife but they share custody of the child.
From my understanding he screwed the ex pretty good in the divorce proceedings.  Supposed to pay half of the medical and  half of the child care plus some other things per divorce decree.  Why she didn't ask for child support is beyond me.  We came into this, way after the fact and just now learning more things.  It seems that just about every time he is supposed to pay his portion of the child care he tells my wife he will pay later or that he will give the money to the ex.   Wife finally talked to the childs  mom and found out he wasn't giving her any money, she was just paying it.  She is just barely scraping by with having lost her job not too long ago but was able to get another.  
My question is if you are on .mil disability can the mom go in to see a Vet rep and try to get something changed so she can start getting his disability garnished for his portion of the support. (without going to court)  I don't know what disability he has but I know he only works cash paying jobs.

BTW, this isn't a we  want our money situation.  I am a former Marine and this type of action is insulting to all of us that go out and do our best to take care of our family and this piece of garbage isn't.   My wife tries to help her out but the mom has done a pretty good job on her own as she has a good family support system.  

Lots more info. wanted to keep it simple.

Any help would be greatly appreciated.  

Unfortunately, the only recourse is through the courts. What is probably worse is the guy might even be getting paid extra for his kid, if he's 30% or more disabled.

Not sure about TX but here in IA i had a simular arrangement with my x wife. Supposed to be 50/50 on everything.
That lasted about 1 month.
I spoke to several lawyer's over the years and they all wanted $5k up front to pursue changing the original court order.

On the other side there is an organization in Iowa called Child support recovery. They provide free legal services to any woman in Iowa regardlessof income.

Have Mom see if he is collecting SS Disability, too.

From SSA website:
When you qualify for Social Security disability benefits, your children may also qualify to receive benefits on your record. Your eligible child can be your biological child, adopted child, or stepchild. A dependent grandchild may also qualify.

I would go in strongly for MYOB in this situation. The likelihood that any party of that type of situation is giving a full and accurate story approaches zero, and you will just be sorry later when you get dragged into their mess.

Absolutely this. Most I would say is for her to revisit the court over the court order she claims exists and let them figure out what's legal and not.

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As far VA garnishment - yes and no.

It gets fairly convoluted, so best to just talk to a lawyer.

More info here:
https://cck-law.com/blog/va-disability-benefits-divorce-child-support/
https://www.disabledvets.com/faqs/can-va-benefits-be-garnished-child-support/
https://www.statesidelegal.org/veterans-benefits-and-child-support-q-and

States can NOT garnish VA Disability Compensation for back child support. Or at least Missouri can NOT do so. Remember that according federal law , VA Disability Comp is NOT considered income. AS others have mentioned, only the federal government can garnish VA Disability Comp.

The state of Missouri tried garnishing my VA Dis. Comp when I fell behind on child support while waiting for Social Security Disability to kick in and also waiting for an increase in my VA Disability rating. Try as they might, the state could not touch my Disability Comp.  So check with your state laws. But I am pretty darn sure that states can NOT touch VA Disability Comp since it is not legally income per federal law. Missouri definitely can't.

Now with that said, I do not know if federal law have changed since 2007 when I last had to deal with child support payments. One my exe started getting money from Social Security for both children, my child support stopped all together. In fact I actually got a refund from the state after they found out my exe was getting money from Social Security while still getting paid child support.

As far as gettin extra each moth for dependents, the VA does not care if the children reside full or part time with the veteran. They are still the veteran's dependents no matter what. I still got paid extra each month for both of my children from the VA even though their mom had primary custody. And that did NOT change even when my exe started getting Social Security benefits for the children either.

Side note: Social Security benefits goes to the parent that the child primarily lives with and also has legal custody. I know this since my exe was getting money from Social Security for both kids until the oldest moved in with me permanently. She go money for the younger son while I got money for the older son.

First off and most importantly is MYOB!!!!!!!!!!!!!!!!!!

Secondly, you are only getting 1/3rd of the story.  There is always his version, her version and the truth.

https://www.nclamp.gov/publications/silent-partners/divorce/

Look and learn