The actor, who reprises his role as Gandalf in Peter Jackson's prequel to The Lord Of The Rings franchise, stepped in on nanny duties to give Freeman some much-needed time with his wife.
Freeman was separated from wife Amanda and their two children Joe, seven, and Grace, three, for the best part of 18 months during filming, and he was grateful for Sir Ian's help when his family finally joined him on location in New Zealand.
Freeman tells The Sunday Times Magazine, "Yes, I got lovesick. My family would come out for a few weeks then go home again, but over an 18-month period I saw less of them than I'd want...
"When they came over to visit, they had the experience of being babysat by Gandalf. So they were read bedtime stories by Sir Ian MCKellen, a man with one of the most beautiful voices in the English language. And that's kind of cool."