I was thinking the same thing re: baby buddies. The only way it could be plausible is if we all had varying lengths in gestation - 37 weeks, 40 weeks, 42 weeks etc....and hence although genders were different, conception periods were different too. Unsure about the likelihood of that though!
When pg with DS2 I can think of two of my Belly Buddies (off the top of my head) who were due almost the same time as me (we were due within days of each other) and they both had girls. They would have definitely been conceived during Aquarius. It's still interesting though