Jake Gyllenhaal loves being an uncle.

The actor is besotted with sister Maggie Gyllenhaal's two daughters, Ramona, six, and three-month-old Gloria, and describes the girls as "extraordinary."

"They are the best thing that happened to my family probably ever," he added.

Jake, 31, admits he can see similarities between Ramona and Gloria and him and 34-year-old Maggie when they were growing up: "It's a similar dynamic between me and my sister to this day. I think we are each other's toughest critics, but we also, I think, love each other's work more than anyone else. Even at this age, my older niece will come up to her [sister] and joke to her, and she'll laugh and then she'll run away and she starts to cry."