Complex sentence: As a foal, he was given the nickname "Junior" by the Martins because of his resemblance to his sire, the Pulpit son Lucky Pulpit, who won three races, including a stakes race.
Split into simpler sentences: As a foal, he was given the nickname "Junior" by the Martins because of his resemblance to his sire, Lucky Pulpit. A son of Pulpit, Lucky Pulpit won three races, including a stakes race.