There are different ways to keep people together while flying.
Kites 
Flocks of Birds 
Matt Nava (Creative Director at Giant Squid Studios) talked about this for Abzû – keeping schools of fish following each other by simple behaviours that led to emergence.
Dragon Conga Lines 
Lotus Leaves 
Sky Formations 
In the game Sky: Children of the Light, people can hold hands as well as piggyback.
Hold hands
(Miyuki has a diamond formation)