Hanson Is All Grown Up -- and Dads of 15! Inside Their 'Awesome Journey' in the 25 Years Since 'MMMBop'

This week's edition of PEOPLE, Hanson brothers Isaac, Taylor and Zac open the story of their rise to fame 

as well as their lives at their home at home in Tulsa, Oklahoma, with their 15 children.

It's a warm May afternoon in Tulsa, Oklahoma, and Hanson brothers Isaac, Taylor and Zac are 

trying to do to do the unthinkable: get their 15 children ranging between the ages of

1 and 19 to smile at the camera during the PEOPLE photo shoot in the recording studio used by the band.

A son from Taylor's family 3 year-old Indiana is particularly difficult to convince.

"Indiana, do not look at the camera!" The group of them all tell himto look away 

, attempting reverse psychological tricks. It does the trick.