When to put a baby in with her sister?

[Bobbin12]

DD2 is 8 months old and still not sleeping through. I think she needs to get into a bigger cot but there is no room in our bedroom and I am worried about putting her in with DD1 (nearly 3) incase I then have 2 DDs not sleeping instead of just 1! Does anyone have any ideas?

[hellymelly]

IME the older child quickly learns to just sleep through the smaller one waking,that has been true for a lot of my friends and for me.We all still co-sleep but dd1 (5) very rarely wakes unless dd2 (2y 10m)is talking really loudly and even then she goes back to sleep easily.

[Bobbin12]

Thanks for that. How old was your dd1 when you put them in together?