getting custody of problem child?

My ss is 6 years old, he lives with his mom and grandmother, but his grandmother is his guardian, because his mom had given up her rights and gave custody over to her mother without notifying my husband. They moved and did not give my husband the address or phone number, after a year without seeing my ss, my husband was able to get the phone number and address. after talking to my ss, he clearly stated that he wanted to come live with me and his dad. that child support should be given back to his dad? How does a six year old know about child support? well, anyway, when he spoke with his ex, she screamed at him and made him cry. she told my husband the "J" has a anger problem and he will be going to a different school, a school for children with emotional problems. "J" is in 1st grade, he told me that he doesnt know his abc and numbers well, I've also heard that he's causing fights with his other classmates, now my husband wants custody, hes sure that's is her and her mother who's doing the damage. what can my husband do to get custody before any more damage is done?

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Vampgirl26