>>34858942All we know for sure in the anime is that
>Mallow and Lana are the same age; they were toddlers at the same time and were the same height back then>Lillie and Ash are the same age>Kukui's class originally consisted of Mallow, Lana, Kiawe, and Sophocles; Lillie enrolled in the school some time later, then Ash enrolledIt's entirely possible that Ash and Lillie are the youngest of the group and that Mallow, Lana, Kiawe, and Sophocles are all older than them and around the same age, with Lana and Sophocles just being really short for their age