But you cannot simply surmise that because a younger sibling outperformed the older in chess studies that some special magic mind sauce called 'talent' exists!
In many situations, when two siblings are both exposed to the same highly enriched learning environment, the younger one seems to achieve even more than the elder sibling.
Example: Mozart and Mendelssohn.
In my own family, my older brother is a professional violinist. But he doesn't play jazz, improvise classically, compose, or play a second or third instrument. He's just really good at playing the violin.
Me, I play four different instruments, I play many different musical styles including jazz, and have composed a significant number of new works.
I don't have special magic brain sauce from God that my brother doesn't have. I just have a wider range of interests that I devote a huge amount of time towards.
He is also a well-rounded fellow, don't get me wrong. But he can only juggle three balls. I can juggle five. Again, not talent. I've just practiced juggling for hundreds and hundreds of hours, while he was on tour playing with the world's most famous conductors.
Because I don't have a performing career at the moment, I have time to work on my golf game and study medieval martial arts.

That's how life works. You only have a certain amount of learning resources. You have to spend them wisely, and learn to love what you learn.