![](/static/253f0d9/assets/icons/icon-96x96.png)
![](https://lemmy.world/pictrs/image/5170ed37-415d-42be-a3e7-3edd79eda681.png)
If “half your age, plus seven” gets you the youngest age society will accept, then, “minus seven, times 2” should get you the oldest acceptable age.
So (18-7)*2
is 22. A mom with a 3 year-old is still a mom.
And if that doesn’t suspend your disbelief, you could still slap on “step” to the relationship label and the script writes itself.
I would have expected studios to use a 3rd party system back then. GameSpy was huge in that era to cover that functionality.