Do you think sperm is 50/50?

Jen
So apparently my FIL is 1 of 12. 9 turned out boys 3 girls. His brother had 1 girl 2 boys. He had 4 boys no girls. My first child will be a BOY... Do you think its impossible to ever conceive a girl ? According to his family my chances are slim to none. Just wanted to know if some of you have a husband who's family consist of majority boys and you ended up having a girl? Is it 50/50 or do some males only produce a certain gender?