Dach...as you know there are 17 months between Olivia and Charlie and I had the same issue.....particularly becuase I wanted to get Olivia out of the hammock in plenty of time for Charlie to use it, and for her not to associate changes with his arrival, IYKWIM?

Anyway, she moved into a cot at 11 months, and from that point on she rarely needed us in the night so it wasn't an issue, and she has never been a co-sleeper (she never wanted to!) so I can really see how that is tricky for you.

When Charlie was born we had been in a new house for a couple of months, so we used the moving house to get her new big girl room all set up, and Charlie was next to us in the hammock. (He has now moved in to his own room).

I guess my advice would be to try & intoduce some new settling techniques now, for Yasin, just so that when you have the new bub, for night feeds etc, you attempt to just focus on one of them?! (Just from experience, night feeds for me are brain dead time, I am hopeless, if I had had two of them in the same room, it would've stressed me out!)

The other thing that a GF of mine has done (she has a 22 month old son and a 3 month old baby girl) is weaned her son off the co-sleeping in their bed, & he is now in his own room totally, but she has a small divan single bed in his room, so if either she or her DP need to spend time settling him, they can still co-sleep with him in his room, while the new baby is still in their room with the other parent....if that makes sense?

HTH?