I found an interesting Australian survey, mostly about childcare. A table at the back shows the hours of work of mothers and fathers, and the type of childcare used (if any). I had a quick play with the statistics, and found the following:
4% of Australian children under 12 have no non parental childcare (childcare includes informal care such as grandparents), and a mother who works >35 hours a week. Since neither of our two children would be included in this statistic (although I work >35 hours a week, they both go to preschool for 2 days a week), I think it’s probably safe to say that at least 1 in 20 of Australian children has a stay at home dad for the majority of their childcare.
I think I would believe his sincerity more if (a) he hadn’t spent the previous (at least) three years in a job which meant he could spend no time with his kids and (b) he wasn’t getting paid a very nice parliamentary pension for the privilege.