I will have to work backwards for this because I have to think about when I conceived the older three LOL.

Baby #4 was conceived on December 24, 2006 under capricorn and was a boy - so that one is wrong
Baby #3 was conceived during September/October under Libra and was a girl - also wrong
Baby #2 was conceived during late January on the cusp of Capricorn and Aquarius and was a girl
Baby #1 was conceived sometime during May/June in Gemini and was a boy