Question

Suppose a couple will continue having children until they have at least two children of each sex (two boys and two girls). How many children might they expect to have?

Answer 1

For the question above, we will use probability.

after 4 children, there is 37.5% chance you have 2 boys/2 girls

after 5 children, there is 62.5% chance you have at least 2boys/2 girls

after 6 children, there is 78% chance you have at least 2boys/2 girls

after 8 children, there is 93% chance you have at least 2boys/2 girls ...

based on this i would say a reasonable expectation would be about 6 children

I hope this answer helped you somehow.