She's not if you read the story again, mother supposedly died/dissapeared one day that's why the kids were looking/waiting for her. So, Chesa is the youngest. You just think she's eldest cause we saw her as a grown adult but, she was sent to the past. But now that she became a baby she cant revert back to being an adult cause she was originally this age at the current timeline

Am I wrong? Lichesia is the older sister of the three boys?? But how is she the older sister and they the youngers ones??