it will happen when you suddenly feel... complete i think thats the word im looking for. it happens quietly at first and you will try to fight it and try to convince yourself no no i really really want a girl, my boys really really want a sister. but you will go out to eat and you will see your boys sitting nicly while a lady nearby with a screaming newborn does everything she can to comfort her baby. you will think, "poor lady, thank goodness that isn't me." and you can look proudly at your boys being little gentlemen
then you can go home and you can say "boys in the bath and brush your teeth." and they will jump to it. while you have a cup of tea or check your email without a toddler screaming "no!"
the next day you will watch your boys play together and you will think, "if i had a daughter what would she be doing right now? would she play with her brothers? or would she play with barbies alone? would her brothers even want a destructive toddler to play with them?
you play music while you clean your house or make dinner and you don't have to live in fear you will wake up a sleeping baby. the boys will get rowdy and dance and chase each other and you will think its great and you won't yell at them to "be quiet! because if you wake that baby for the love of god i will sell you to band of gypsy women." (yes i have said that before although my children think a gypsy is a dog, we had a dog named gypsy once so they think living with dogs would be great)
you will tel yourself over and over no this is what i want, i want a daughter. but there is a little voice in the back of your head that says, is it worth all the sleepness nights and starting over again just so hear, "yea it has a vagina" what if i hear, "sorry lady it has another penis" then if you are really crazy like me you will imagine you hear it has both, that was my dream last night anyway, but we'll save that for another topic. when the last baby gets potty trained you will realize how much money you save on diapers and wipes and not washing sheets everyday from leaking. you will try to convince yourself you can afford another baby but then you will think, but i can put the boys in karate or swimming lessons too.
thats when it hits you and yes thats probably why it took me until my oldest was 10. right now your children are little and you have a new baby so you can't even imagine what im saying is true. my baby is 9 months yes still little but almost 1 so she was just starting to fit in nicly with the girls. if you can make it 2 or 3 years without getting pregnant you will start to see what i mean. in the meantime i enjoy your new baby!