Im of the mindset that if it didnt happen/revealed on panel then its not canon and that includes letter pages. I can almost guarantee you that no writer is referencing those when it comes to writing characters, hence why it shouldnt be a shock that it hasnt come up again
The ages vary but generally speaking they were seperated when they were 6 and 8. Alex grew into his athletic prowess but as a 6 year old, he wasnt gonna take on his older brother