Witnessing the birth of his child made Heath Ledger rethink his previous definitions of masculinity in a way that playing a gay Wyoming sheep herder didn't. He ruminated a bit on the topic with a reporter from his hometown paper, the Perth Confidential.
Also, he sounds like he's doing a lot of the heavy lifting around the Williams-Ledger house: "My life right now is I wouldn't say reduced to food, but my duties in life are that I wake up, I cook breakfast, clean the dishes, prepare lunch, clean those dishes, go to the market, get fresh produce, cook dinner, clean those dishes and then sleep if I can."
Admirably close to the "Everything But Breastfeeding" gold standard, but no mention of changing diapers. Maybe he was just waiting for good old-fashioned, Aussie-style flushable gDiapers to go on sale online.