You cannot increase or decrease your number and counts; generally you may enhance or encourage or tries to increase the number; but this is not up to you.
It is up to God to give boys or daughters to whomever He likes.
Read it in the Torah (or the Old Testament, Book of Levites (or Leviticus or Priests), chapter 26:
If they work according to God's commands --> He will give them more boys and will increase their number;
While if they work contrary to God and disobey Him --> He will increase their females and decrease their boys and will decrease their number.
See my post in the thread: God does not wrong anyone
Comment: One of our professors in the past told us once an example: his father produced ten sons, while the king, the minister and the prime minister and the guardian of the king of Iraq had only one son for each.
The workers and peasants usually have more children; those who toil and work hard with little income ... these usually have more offspring; while the luxurious usually have no or very few children : one boy or girl.
E.g. kings of England and other countries: each usually have one or no child, while hard workers have ten sons for example.