Any party to the purchase must be a genuine first-time buyer. This means that a couple where one partner has not owned a house but is moving in with someone else that has owned a property before would not qualify if the house is bought jointly. It also means that parents who are home owners (or have previously owned a home) can no longer buy together as joint purchasers with their children to help them get on the property ladder, if they want to take advantage of this stamp duty exemption.
Work around options may start coming to light but at present the way for parents to assist with homebuying whilst benefiting from the Stamp Duty exemption would be to opt for the guarantor route. This means that the income that parents earn can still be assessed in lending calculations, but critically as the guarantor would not be listed on the title deeds the child would still qualify.