Hi there. I present to you a challenge inspired by a book i read. (sorry if something like this already exists)
instructions:
-make a married couple in CAS

-move them into any lot you like- but it can't be purchased via money cheats. (space for a family grave may be useful )

-make them have children. you may want to have quite a few because...

-...once every a (sim) week, you roll a pair of dice. Count (top to bottom) the sims icons on the left, for the total you got. Whatever sim you land on, you kill. This means two sims die per week.

-repeat this for 7 generations.

Rules:
-no cheats- however, you can cheat to age up a sim if it they are too young to kill (baby,toddler)
-No adopting children (too easy!)
-nobody can move out (for this, you may find a larger households hack useful, but you don't have to use one)
-kill them any way you like, apart from old age.
-only one sim can have a job at a time. You have to find other ways to get hold of money (such as gardens or busking)
-only sims are killed if you land on them-pets don't count.

No children out of wedlock- widows and widowers can remarry.
You lose if all your sims die, or if you are left with one sim that cannot reproduce (e.g an elder female).
I won't have a point system, but feel free to make up your own.
Enjoy

what happens if you end up having to kill both of the parents in the same week?

Yeah if they try for baby 1st night, 4th night they have child, baby grows up on 6th day, you'd have to immediately grow it up and kill it along with the other parent, then he/she would keep having to remarry. And there is a good chance the parents would be killed on the first week.

you should make the challenge where you can start with 2 children in CAS

You should make it every two weeks.

That way, you have plenty of people to kill.