The sleep training. Ugh.
First step actually went pretty well - we removed Nolan from the equation. I'm scared that is what has improved things drastically, as it is unfortunately not a permanent solution. Nolan sleeping in a play pen in big sister's room isn't really great for the two of them, whether it's great for Asher or not. But it's working for the time being so we'll leave it a few more days.
Second step - put Asher in a sleep sack. He looks like a lovely little princess in the borrowed pink sleep sacks we have, but he sure doesn't seem to mind. I don't know for sure how much help it is giving (because this started the same night we moved Nolan out) but I can imagine that this gives him a small sense of swaddling, and therefore helps with the nighttime startling that often wakes and upsets him.
Third step - let him cry. For the first few nights this wasn't required as he seemed to do really well both without Nolan and with the sack. But the past couple have not been so great. One night we had to let him cry (in 10, 15 and 20 minute increments) for over an hour before he fell asleep, and last night we had to do the same thing at 4am (Our pooooor tenant! I think we need to leave some beer outside his door!).
As hard as it is to let him cry (especially when he cries harder after we go in to quickly comfort him), it seems to be working. We'll see how many nights it takes before he breaks the cycle completely. Considering he doesn't do it every night, it may take a while.
In the mean time, we're all getting a bit more sleep, stressful as it is, so I'm thankful for that!