I just wanted to update that thinking of bedtime starting much earlier, and assuming that it is going to take an hour longer than I’ve planned has helped A LOT just over the last few days! I’ve also been working in roughhousing/giggles/connection games throughout the evening, but I haven’t specifically focused on separation anxiety and there still is such a big change. They both were asleep by 8:30 tonight which hasn’t happened in months.
My youngest still naps, so I have also been trying to give her good listening time when she gets upset at naptime. I can really give her my attention then, without worrying about her brother getting riled up, and so I’m hoping that if she can release some big feelings at naptime then they won’t come up as often in the evening. So far, so good!