The stallion must be listed with the APHA, whether it's a Quarter Horse, Paint or Thoroughbred. It's a one time fee of I believe $75 and it allows the horse to have registered babies through the APHA.
If the stallion was NOT listed on the stallion list through APHA, you have to pay the $75 to get him listed, to get your foal registered. DNA is also required for all stallions listed.
Say the AQHA has the horse registered through them, APHA can contact AQHA and have the DNA record transferred so you don't have to pay the extra fee.
But, if the stallion is APHA registered, but not listed with the stallion listing, you'll need DNA from the stallion. And since the previous owner doesn't own him anymore, this may put you at a standstill. I say may, because I'm not 100% sure since APHA does not require horses registered to have DNA profile done the way AQHA does.
"The greatest pleasure of a dog is that you may make a fool of yourself with
him and not only will he not scold you, but he will make a fool of himself too."