Here’s an interesting chart I found:

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Plenty of information on mums available in Australia, not so much for dads. The average age for first time mums in 2020 was 29.7, with the largest proportion (38%) between 30-34 years old. Anecdotally, I was a first time dad at 34, and my wife at 36.

Very anecdotally, but just from looking around and the people I know, it would look like a bell curve with the peak in the mid 20s (say 25) and a pretty good percentage of them being around eight years either side, and a tiny few further out in both directions.