Mine shared when 12 months and 3 years, DS still wakes sometimes but doesn't wake DD unless it's close to morning e.g 6 etc. She would sleep a little longer in morning if he didn't wake early. She never wakes him. No real tips mine have always not been disturbed by noises as noisy flat, when DS in with us could go into bed and talk etc and wouldn't wake . We didn't try putting together earlier really just due to visitors and easier for me to deal with him overnight in our room.