Complex sentence: Jesús Javier, at the age of 18, worked under the ring name "Oro" and his brother used the name "Plata" (Silver) with identical masks, only one had a gold pattern and the other had a silver pattern.
Split into simpler sentences: Jesús Javier, at the age of 18, worked under the ring name "Oro" and his brother used the name "Plata" (Silver). The duo wore near-identical masks, the only different being one had a gold pattern and the other had a silver pattern.