you get up to 12 weeks of fmla every year as long as you have been with the company for at least a year. further details than that you would need to look up the law and ask your hr department. part of the reason why I'm only taking 8 weeks instead of 12 is because I want to leave some time in case I have to take leave for something else.
under FMLA you can take up to 12 weeks off without losing your job. but they don't have to pay you at all, so you will want to think of that. some employers will give you longer leave, which is cool. I'm going to be taking 8 weeks off, that is what I chose.