Irish Twins? Anybody that can give me some insight/advice?

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I just gave birth to our baby boy on Dec. 10th. My SO already has baby fever & is asking if we could try for another. He would like to try around March when our baby boy is 3 mos so that they have birthdays around the same month. When I sit & think about it, I get very happy & excited.. but there's moments where I can't picture myself giving my attention to anyone other than our little boy. Any mothers have Irish twins? How hard was it, how did you manage to keep it all together, WHILE still keeping a healthy relationship? Any advice is appreciated. (Also, I know it's not "suggested" but I want some insight)