It's entirely likely Heath Ledger and Michelle Williams learned their parenting skills in Calgary last year on the set of Brokeback Mountain.

In Ang Lee's Oscar-nominated western, Ledger and Williams play the tragic couple who must deal with the realization he is in love with another man.

To make things even more complicated, their characters have two young daughters.

Calgarian Hannah Stewart, who was four-and-a-half years old at the time of shooting, plays the oldest daughter, Alma Jr.

Her father Dean Stewart was on set the whole time Hannah was shooting.

"I was so impressed with the patience both Heath and Michelle had with the kids," recalls Stewart.

Ledger and Williams, who started their relationship on the set of Brokeback Mountain, welcomed a daughter, Matilda, last October.

"It was really neat watching that relationship blossom. They didn't really know each other before starting the film," says Stewart, who says young Hannah may have bolted from the production her first day on the set had it not been for Ledger.

"Hannah has very blond hair so they had to darken it. They got half of it done in the make-up trailer when she leapt out of the chair and refused to continue.

"Heath walked in and completely calmed her down. It was remarkable. It was the beginning of a great trust and friendship between them."

Stewart recalls one day he and Hannah were sitting on the steps of her trailer when Ledger passed by.

"Hannah just nonchalantly called him daddy. Heath buckled over laughing."

One of Hannah's major scenes was filmed in Fort McLeod.

Ledger had his motorcycle shipped in from L.A. and had been polishing it for hours when Hannah came over and asked if she could help.

"He gave her a rag and she proceeded to undo most of what he'd accomplished. He found the humour in it," says Stewart.

Stewart says he is grateful all of Hannah's scenes appear in the film.

"So many local actors and extras had their scenes cut, which is the reality of the business, but Hannah's scenes are all there.

"Even more exciting for us, snippets from two of those scenes even appear in the trailer for the film."

Hannah has seen herself in the trailers that run on TV, but she will not get to see the whole movie for a long time.

"I think it is a very beautiful, challenging film, but she won't be ready to handle the (gay) subject matter for quite a while."