When walking your baby wyvern don't think to yourself I'll just take it for a little swim through this lake. Because as soon as it hits the water it starts to fly and it won't stop! When you whistle to stop it just starts to fly off into the sunset. Say good buy to your wyvern and all the milk in its inventory.
This Is my guess/hypothesis if you leave a wyvern egg sitting on its nest for a long time and you get it after so long you have a big chance of getting triplets. Trust me I did it my first wyvern egg and I got triplets. Up so people know if they dont know they wont do it and get triplets