Emiliano De Pablos Top Spanish producer Nostromo Pictures, which is behind Netflix hit “Through My Window,” is partnering with Beta Fiction Spain to launch “Hermano Caballo,” a documentary by Marcel Barrera, director of “Mediterraneo: The Law of the Sea” and “100 Meters.” “Hermano Caballo” marks the first documentary produced by Nostromo Pictures and also the first handled by Beta Fiction Spain, the Spanish arm of Jan Mojto’s European studio Beta Film, which launched last year. The documentary focuses on reknowned Catalan wrangler Santi Serra, developer of a natural training technique based on creating bonds with horses and learning through play.