Natalie Portman and Benjamin Millepied are determined to be the “best co-parents they can be”. The Oscar-winning actress and Benjamin, 46, recently finalised their divorce, and the former couple are now focused on co-parenting their children – son Aleph, 12, and daughter Amalia, seven. A source told PEOPLE: “Her biggest priority has been ensuring a smooth transition for her children. “She and Ben really love their kids and are equally focused on being the best co-parents they can be. Nothing is more important.” Natalie, 42, filed for divorce from Benjamin in July, and although she initially st…