updated 06/02/2014 AT 2:35 PM ET
•originally published 06/03/2014 AT 11:45 AM ET
“When you do have a bond like ours, it is more like a partnership, not necessarily a brother-sister thing,” Julianne, 25, tells PEOPLE. “You know when someone needs each other.”
Now, the two are back together again and spending lots of time rehearsing for the tour, practicing up to six hours a day. Derek says the long hours have definitely made them closer. “When you train together and travel together the relationship becomes very supportive,” he explains.
The Utah-bred siblings are most looking forward to the tour’s stop in their hometown, where they will perform for their friends and family.
“Our parents are very cool,” Julianne says. “They are not super involved like stage moms and dads, but they are very proud.”