One Piece S04E70 - The Fated Parent and Child! The Mother's Name is Olvia!

Robin continues talking with Saul, and Saul is shocked to learn that Robin is Nico Olvia's daughter and that he is on Ohara. Olvia returns to Ohara to warn the other scholars that the World Government's forces are headed there. She decides not to reveal herself to Robin, not wanting her daughter to be branded a criminal because of her. CP9 arrives on the island, capturing Olvia and rounding up the scholars.