Question to Dunford regarding the Marshalls

Hi Andrew, 

I just checked the Marshall twins' stats on Cricinfo.. and it seems
that James' average is superior to that of Hamish and also that James
has a 200 in his name.. Why is that Hamish has been preferred over his
twin bro' in the NZ Team setup?

Are these two good enough to play together for NZ someday?

TIA.

--Srini.