When you pay someone else's school loan for them it is the same as gifting the money to them and they use it to pay the debt. Gifts to any one person is limited to $15K per person ... amounts in excess of that require the giver to file a gift tax return.
Please do not post separate questions about the same issue. It's too confusing and hard to follow, and hard to see the whole picture, if information is scattered in multiple threads. If you want to add more information or post a follow-up question, add a comment to your original question.