For truly independent events you're right, but there are environmental / biological factors that might influence the ratio.
Well, they should still be independent events. From what I can tell, that would just slightly change the ratio of boys to girls. I couldn't find any case where it seemed like having girls affected the rate of having more girls, and there shouldn't be any effect for children born to different families.
Jesus give these folks condoms as a giftHere is the other side of the coin that evens it all out.
This family had 14 sons in a row: