My in-laws are the same. Two kids is fine, maybe a third if the first two are the same gender, but that better be the max. They had such a fit over #4 that DH is going out of his way to hide this pregnancy and covering me up in big, sloppy hoodies when they are around. I'm kind of sad because I want to announce the twins. DH is just too afraid of their bad reactions to allow it yet.
My blood test said I'm having girls, but it's not as accurate for twins so we're waiting for ultrasound to confirm it. Praying at least one is pink.