How many family members does a Mexican immigrant usually bring into the United States?

As many as they can. * That would be an impossible question to answer. However it is certain the number is less than the Irish immigrants, the Puritans, the Mayflower Pilgrims, the Germans and Polish Nationals, not to mention African slave ships (an indisputable immoral action condoned by the US government). FYI, there are Mexican Nationals in the US legally and therefore they can legally sponsor other family members.