There is only 20mths between our 3 and when Erin came, Lindsay was still in the cot in his room (he has never slept with us in our bed). Erin was in the bassinette in our room until she was too big (3mths). Then she went in to the cot and Lindsay into his 'big boy bed'. They never seemed to wake each other up luckily. Is Yasin in a cot or a bed? Maybe this could be your chance to get him excited about a big boy bed. Let him help you pick sheets etc to make him feel grown up and important. That way he may want to stay in his own bed. When Bubby is big enough for the cot, maybe they can share a room and Yasin will still have a sense of someone being in the room with him.

When any of ours wakes in the night, I aways sat beside them to comfort them and get them back to sleep, without having to put them in our bed.