Just thought I'd point this out.

If you take a look at this updated list of the bladers' birthdays:

And if we assume that everyone is the same age around the time frame of Burst and Evolution...

DAIGO IS THE OLDEST OUT OF EVERYONE!

AND XANDER IS ONLY THE FIFTH OLDEST!

EVEN UKYO IS OLDER THAN HIM!

And so...

I'd like to think that Xander is the type of big brother that is more than willing to give his younger siblings a piggyback ride, and Daigo is the type that is more than willing to deal out punishment to either his younger siblings or whoever made them cry.

There's definitely a difference between being the oldest and just being big.