Who? My parents.
Their reaction? They'd probably insist on me not giving it to them and spending it on my daughter, which I can totally appreciate. They absolutely love me and my daughter, and they want her to have the best things and opportunities she can.
Why? I owe them more than I think I can ever repay them. I know what their reaction is because they've repeated that response every time I've tried to pay them back, but the fact of the matter is that I owe them. They have gone well out of their way to support me, particularly in instances where I really didn't deserve it. It's not enough to clear my tab to them, but they deserve to have some of that money back. They've invested so much time, effort, and actual currency into me that they deserve some sort of return on it.
Sometimes parents are turds, haha. I know mine have supported me a lot, and continue to, and it doesn't go unappreciated, which is also part of why I chose my parents as well. Thanks for your thoughtful comment! :)