How can I get money from union painters pension fund that employers paid into for ex husband that the pension fund won't release and can I get that money because my ex still owed back child support on his grown son at time of his death?

Many pensions END at the death of the person receiving them. Its not like it was a savings account. If he died two weeks after starting it it ends... nobody else gets a dime... if he lived to 110... he would get it until the day he died. Thus it is not part of his estate. There are no remnents anyone else is entitled to after his death. I assume his pension was that type. One of my Uncles had one like that... ZERO survivors benefits of any kind for my aunt that survived him. Not all defined pension plans are like that however.

Now if he had a 401K plan... that would be different, as there would remain a cash balalnce and it would be part of his estate.

If he owed for support file a claim against his Estate - as Smoothy said, his pension probably died with him.

When you say ex husband were you married to him during the time the pension was being accumulated? Was it part of your divorce settlement?