Suppose generation 0 is the parents, generation 1 is the generation that includes the unexpectedly dead child, and generation 2 is the generation after that (the children of generation 1).

If you are asking about the effect upon the size of generation 2, then it depends upon the people in generation 1 who didn't marry and have children.

Take, for example, a society where generation 1 would have contained 100 people, 50 men and 50 women, and the normal pattern would have been:

• 10 women don't marry
• 40 women do marry, and have on average 3 children each
• 30 men don't marry
• 20 men do marry, and have on average 6 children each

And the reason for this pattern is that each man who passes his warrior trial can pick and marry 2 women, and the only way for a woman to marry to be picked by a warrior.

In that situation, having only 49 women in generation 1 would make no difference to the number of children in generation 2. The only effect would be having 40 women marry, and 9 not marry.