S.S.
There are a couple of great books out there--you can even check them out at the library. One is Healthy Sleep Habits, Happy Child by Marc Weissbluth. The other is The Happiest Baby on the Block by Harvey Karp. Both have excellent suggestions for healthy sleep habits, but the main thing to remember is DO WHAT WORKS FOR YOU. One other poinbt, is since the twins were sleeping well, and are now at a major developmental point, I'm guessing they're experiencing what some call "wonder weeks." These are basically times when things (mostly sleep) regress because of some other milestone. There's actually a book on it, but I can't remember the actual title. Anyway, both my boys are super-prone to sleep regression at milestone points: learning to crawl, walk, verbal breakthroughs, etc. Even my 4 year-old gets it! Hang in there!