Sisters are built-in best friends — and Aliannah “Ali” Hope Simms is lucky that she has two! Teen Mom 2 star Leah Messer‘s daughter was diagnosed with Titin’s muscular dystrophy back in 2014, and she is constantly facing and overcoming struggles related to the disorder as she gets older. But thankfully, the 9-year-old has the support of an awesome mommy and her sisters Aleeah Grace “Gracie” Simms and Adalynn “Addie” Faith Calvert. Leah, 26, opened up about her daughters’ special relationship and how they all support each other through difficult times. Scroll through the gallery for more details about Ali, Gracie and Addie’s strong sister bond!