his, her, or their horse
Tom montó su caballo y se fue.
Tom mounted his horse and left.
Yanni montó su caballo hasta la mezquita.
Yanni rode his horse to the mosque.
Se encuentran en la calle principal, su caballo acaba de morir.
They are on the main street; their horse has just died.
— State and Main (2000)
Al entrar al jardín, su caballo tropezó con un cable tendido entre dos árboles.
Upon entering the garden, his horse tripped over a cable stretched between two trees.
— Das weiße Band - Eine deutsche Kindergeschichte (2009)
Su caballo saltó sobre la cerca.
His horse jumped over the fence.
¿Qué ha sido del jinete y su caballo?
Whatever happened to the rider and his horse?
— El señor de los anillos: Las dos torres (2002)
Jackson se cayó de su caballo.
Jackson fell off his horse.
Mary adora montar su caballo.
Mary loves riding her horse.
Tom cuida muy bien de su caballo.
Tom takes very good care of his horse.
Disfrutaba con la idea de recorrer caminos en su caballo.
He enjoyed the idea of traveling roads on his horse.