The Heirs

The collective term for the Davidson children; Mai, Matt and Megan, this is a title bestowed upon any being who is next in line for the Charmed Legacy. Should the Halliwell Sisters, Piper, Phoebe and Paige die without leaving having a child, Mai, Matt and Megan inherit the power through the Warren bloodline and become the new Charmed Ones. Due to an unforeseen problem in the family of the original Charmed Ones (Prue's death and Paige inheriting), the power of the Eldest Sister belongs to Paige, and will pass on to the next oldest descendant in the next generation, being Wyatt. The power of the Middle sister will pass onto the eldest of Phoebe's children, while the power of the Youngest Sister will pass onto Paige's eldest.
Due to the birth of Wyatt Halliwell, the power of the Eldest Sister has an Heir, meaning both Paige and Wyatt would have to die for Mai to inherit her position as a Charmed One.