Fmla for father

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So i will be a SAHM to take care of baby full time. My SO works and is doing paperwork for fmla. He told me there has to be a primary and secondary parent. Primary gets 6 weeks pto and secondary only gets 2 weeks pto. He said there has to be a name on each line. Why aren't we both considered primary? Anyway the real question is yes maybe i would be considered primary but on paper could we just put him as primary so he can get more time?