I had one that was jealous of the new baby after a parent died. Also had one that was said he was lonely and went and sat by the shed.
It happened to me three times. the first was while the parents were still alive.
second the one parent died. And third, his mother died his father was 60 and he felt jealous about "the new baby"(!) and a second later he was "happy"about the new baby who didn't exist. he was the youngest kid too.