I have two kids and do basically this. I usually work from 11 am or so until 5-6 pm, then from 11 or midnight until sometime between 2 and 4 am. If one of the kids needs before 4am I usually handle it, after 4am my wife usually takes it. Kids are usually up between 9 and 10 am (I guess we're all late risers - not sure if it's genetic or learned) but if they're up earlier my lovely wife lets me sleep.
That sounds like you have a fairly consistent schedule though; the person I was commenting about made it sound like their sleep varied completely (they just stayed up until they were tired and then slept until they were rested).
Of course, many schedules will work for families - my point was that you need to have one if you are going to function in a multi-person family.
