I was 20 when I had my first son, and 23 (almost 24) when I had my second son. I'm 36 now. My oldest son will be 16 in a few weeks. Also, I'm a great-aunt to a toddler. I was an aunt at 12 because I was the youngest of 5 kids. My sister who was the closest to my age, is 4 years older than. My oldest brother is almost 11 years older than me. I also have an aunt who was literally an aunt before she was born. She's younger than 2 or 3 of my cousins.
As far as the game is concerned, sims age faster through the earlier stages. On normal lifespan, the child and teen stages are only 14 days. Whereas the young adult and adult stages are around 24 days each, although I'm not 100% sure on the exact amount.
