My fraternal twin boys are 22 months. Both of them are generally healthy (no special needs, no disabilities; both intelligent, playful little guys). They sleep in the same room, both still in cribs. We keep a fan running at low level during sleep times for the white noise, it's fairly quiet in their part of the house, and the windows are pretty well dimmed with blackout curtains although some light does get through. Both go down pretty contentedly for a nap around 11:30am, and to bed around 7:30pm.
The challenge is in how long they sleep. A is on a much shorter sleep schedule than B. He wakes up from his nap, on average, at about 1pm (about a 1.5-hour nap), and wakes up crying at least once a night, either at about 12:30am or about 4:50-5:15. At 12:30, the only way I've found to get him back down is to rock him back to sleep. At 4:50-5:15, there is no going back to sleep and if left alone, he cries and screams until his brother wakes up. Our current MO is to get him out of his crib before he wakes his brother and lie down on the couch with him until a more reasonable hour, like 6; he'll either nap on one of us on the couch or lie there pretty contentedly for a while being cuddled, but it doesn't do much for our ability to sleep. Currently he has a runny nose and intermittent cough, which are not helping matters; we have amped up the humidifier and elevated the head of his crib.
B sleeps a lot more. He naps either until woken by his brother at 1:15pm or until 2:30 (if I sneak in, get A out of the crib, and take A away); if he sleeps less than 2 hours he's pretty cranky upon waking. He sleeps through his brother waking up mid-night. In the mornings if not awakened he'll sleep until 6:30 or 6:45am, sometimes 7, but he has been known to get up with his brother at 5:15 and be nice and cranky around 10:30 because he woke up too early.
How can I help A sleep longer? Up until now I've been a devoted Weissbluth follower, but CIO is less effective when A can credibly threaten to wake B at 5am and I know that, if allowed, B will sleep longer and be happier. All thoughts are welcome!