Casey Affleck says Jennifer Garner is "the perfect aunt" to his children.
The 43-year-old actor is father to Indiana, 15, and Atticus, 11, and has said Jennifer - who was formerly married to Casey's brother Ben Affleck, with whom she has Violet, 13, Seraphina, 10, and Samuel, seven - is an "amazing" addition to the Affleck family, even if she and Ben are no longer married.
Casey - who has his children with ex-wife Summer Phoenix - said: "Jennifer has been amazing. She's just the perfect aunt. She's so caring and sensitive and never forgets a birthday. She's awesome."
And the 'Manchester by the Sea' star also had good things to say about his older brother Ben, who is a "great role model" to his children.
He added: "[Ben] is a really great role model for them and the way an uncle should be. He pops in and out and takes them to a game or just whatever."
Casey hopes his close relationship with the 'Accountant' star, 46, will help bring a positive influence on his sons in their own bond as brothers.
Speaking to Us Weekly magazine, he said: "You can tell your kids what to do, but they don't really listen. They're way more likely to be like what they see. They're going to imitate you. I could tell them not to fight, but I'm going to have a much bigger impact if I'm able to stop the video when me and Ben get into a fight and resolve it.
"I try to let them see those types of things and not just be like, 'Hey look. Ben and I are great friends. You guys should be great friends too.'"