The Chaos Monster (Secrets of the Sky #1‪)‬

From New York Times bestselling author Sayantani DasGupta comes a new series in which everything is connected to everything, and it's up to twins Kiya and Kinjal to save it all.
When 10-year-old Kinjal hears a strange noise in the middle of the night, he grabs his twin sister, Kiya, and the two go searching in the forest at the edge of their new house. There, they find Snowy and Midnight, two winged pakkhiraj horses from the Kingdom Beyond Seven Oceans and Thirteen Rivers who have come to this dimension to seek help -- bees are disappearing, along with the nectar the pakkhiraj horses need to survive.

Whisked away to a magical realm, the twins must use Kiya's scientific skills and Kinjal's love of books and language. But then they discover that the disappearance of the bees is more nefarious than they thought, and the plot goes all the way to the top.