Lizzie is scared of thunderstorms, so her older step-brother Derek is there to comfort her.
Young Edwin Venturi is afraid of thunder, so he goes to his big brother for comfort and Derek turns on his big brother mode and protects him from the thunder and lightning.
Gabe Duncan is worried about his little sister's behaviors, it's because their mom Amy is having another baby, so Gabe has a big brother to little sister talk with his baby sister Charlie about the new baby.
Bobby Brady is afraid of thunder, it's a good thing he has 2 big brothers to protect him and make sure he's alright.