After causing havoc in the universe and saving it from destruction, Marvel's "Guardians of the Galaxy" are back in a new adventure that takes the unconventional group of friends on a quest to discover their family ties.

"Guardians of the Galaxy Vol. 2," which begins its international rollout on Tuesday, sees roguish thief Peter Quill, green-skinned warrior Gamora, the muscle-bound Drax, mischievous Rocket Raccoon and baby tree-alien Groot split up after being pursued by a gold-skinned villain named Ayesha.

The plot centres on Peter's long-awaited reunion with his father, an ancient god called Ego (Kurt Russell), who is the life force of a planet, and his tense relationship with his adopted father figure, the fin-headed Yondu (Michael Rooker).

"The most compelling way to find out something about a person you're interested in is to explore their relationships," Chris Pratt, who plays Peter, told Reuters.

"I can't think of too many movies or stories on the screen that have honoured that type of relationship, so it's really kind of cool if you like a contemporary family story."

"Guardians Vol. 2," once again written and directed by James Gunn, comes after the surprise blockbuster success of 2014's "Guardians of the Galaxy," which ushered in a new cadre of unlikely heroes into Disney-owned (DIS.N) Marvel's expanding film franchise.

Following the catastrophic events of the first film in which Groot sacrifices himself to save the Guardians, the sequel sees the powerful tree alien as a baby sapling, changing the dynamic between the five heroes.

Baby Groot offers up comedic relief during high-stakes scenes, such as a battle with a giant monster in which the tree sapling dances his way through the chaos and delivers tiny roars.

"Having a child in the group just leads to a even bigger sense of a family," said Dave Bautista, who plays Drax.

After spending much of the first film trying to kill each other, warring sisters Gamora (Zoe Saldana) and Nebula (Karen Gillan) find themselves in close quarters in "Guardians Vol. 2" and faced with their underlying hatred towards their adopted father Thanos.

"They went through something very traumatic and they dealt with it in different ways," Saldana said.

Gillan added that the "angry, bitter and twisted" Nebula is more sympathetic in the sequel.

"We start to see the cracks in her exterior and we learn about her bad relationship with her father and her sister and all the layers are chipped away," she said.