Gift-giving customs vary from family to family, so this is a personal decision based on your own family’s gift-giving traditions and expectations. But if your parents are happily married and you want to acknowledge the union that brought you into this world, emphasize the nature of the occasion by buying them a joint gift they will both appreciate, whether it’s related to shared interests, experiences, or tastes. Or you can keep it simple and offer them a bouquet of traditional anniversary flowers that varies according to the number of years they have been together.