Mother-and-stepmother so is called because, that one side leaf (the lower) - soft, warm. And the second-the top-glossy and cold.
https://images.golos.io/DQmR22FFQNud66QR9vKViYrbwsi8FqUFCubg8FifWSGLs6n/%D0%9C%D0%B0%D1%82%D1%8C%20%D0%B8%20%D0%BC%D0%B0%D1%87.jpg
Although, as we know, mother and stepmother are different. Cinderella's not very lucky. Or Vice versa, really depends on how you think.