It is true that having two kids (or more) changes the family dynamic immensely, starting with sleep. Four individuals with different sleep schedules can be overwhelming, but if you consider this an engineering problem that can be "solved", there is hope. And that's exactly how I decided to handle it: to find a way for everyone to get their sleep on without adversely affecting anyone else. We did this with Moses too, but it was simpler then.
The first dimension is the "how much" of sleep: Nelson is still on a 3-hour cycle all day long; Moses sleeps from 7-8pm to 5-6am (10 hours); Angelene needs 8 hours; and I need 4-5 hours. Night gives us only 12 hours, so the problem to solve is how overlaps will work.
The second dimension is the "when" of sleep: if Moses goes down at 7:30pm and is out for 10 hours, we won't see him again until 5:30am. For Angelene to have 8 hours of sleep, she'd have to hit the sack at 9:30pm and wake up when Moses awakes. But before she goes to sleep, she'd need to feed/change Nelson at 9pm, and set him asleep. I can get my 4-5 hours of sleep then if I go to bed at 7:30pm with Moses and wake up for Nelson's next feeding at midnight. I would do the two night feedings (midnight and 3am) with pumped milk, and he would resume normal breastfeeding at 6am.
Notice how Moses' sleep schedule is really the pivot of this whole plan, not Nelson's; if it's off, we suffer. The other key is the 9:30pm-midnight block when all 4 of us are asleep: if we miss this window, toss the plan out. But we have an advantage in the fact that I am a short-sleeper and night owl, which I can bring to bear for this plan to work.
The third dimension is the "quality" of sleep we each get, measured by how many times we are interrupted in our allotted blocks of sleep time. I reckon sleep interruption is practically worse than foregoing sleep altogether, so we want to limit that number. As parents though, we can hear our babies' squeals in our deepest sleep, and are bound to awaken thus. So our solution: Nelson care happens downstairs so that whoever is sleeping upstairs can have quiet (as in, forget the bedside bassinet). The only hiccup is the 9pm-midnight window, when Nelson is quietly brought upstairs to our bedroom (presumably already asleep). I normally do not hear much of that, although Nelson's been quite restless and loud some of the nights that I awake. Angelene then uses earplugs so she won't hear much of the midnight waking later. When I wake up a little while before midnight, I quietly take Nelson back downstairs.
The orchestration can be a hassle but it pays off when it all works. To help it work, Angelene must pump so we have reserve for the night feedings (or we'd need to use formula), and fixing two extra pumping sessions in a 3-hour cycle can be tricky. Sickness cannot happen because it throws the whole dynamic off. Outside commitments are foregone or limited to allow this orchestration to work. And we must stay on top of things at all times, including eating all meals of the day on time.
Surprisingly, this plan affords us unexpected opportunities: we can have breakfast and dinner together, since those are the junction points on which the night hinges (6pm and 7am). An early start allows me to be back home from work early enough and spend time with the family before night kicks in. The midnight-6am chunk of time (minus 3am Nelson feeding) turns out to be a great time for me to work on personal stuff, read, do some programming, etc. This is when you are likely to see responses to emails and other communication. I have sometimes taken another nap towards the morning, but I like that there is some predictability in the mayhem, that sleep depravation can be avoided with a little engineering creativity.
