Yes, you report it as a gift. If you later pay it back, you committed fraud.

[edit] to clarify what may be a point of confusion:

Rich parents are often in a position to comfortably gift their kid(s) tens of thousands of dollars for their first down payment.

Non-rich parents are more often in a position to somewhat-uncomfortably “gift” that money. It’s a gift on paper, but it’s actually a loan and they need the money back eventually (maybe for the next-oldest kid to borrow for the same purpose, lol). That’s when it’s fraud.