Night Mist is an orphaned young colt Luna bumped into in the city of Canterlot. While seeing he was a bat pony alicorn was surprising, his tiny foalish form, and timid personlity won her over. You could say maternal instincts kicked in, and she adopted him as her son. Luna let’s her new son nurse from her to help strengthen her motherly bond with him, and believes that her son should choose when to ween himself. Even though his fangs have already come in, they are too soft to cause Luna any discomfort. And she finds the scene cute when he nurses.