Twins sleeping through the night?

My twins are 7 weeks, age doesn't need to be adjusted because they were born at 37 weeks. They still wake up every 3 hours to eat and they sleep in the same crib. When they wake up in the middle of the night I don't talk to them and keep it dark in the room. They sleep in Halo sleepsacks and I don't change their diaper unless it's poopy. Anyone have any advice on getting longer stretches of sleep?