I was under the general impression that cats don't meow to each other although they communicate in different ways.
But last few nights at around 1am ginger boy has been meowing like crazy, then going back outside, then coming back in, repeating, until tabby boy comes in- then they will both go to sleep. There have been other instances where one has come in meowing and then stop when they see the other is already inside.
I suppose it's possible they're meowing to US to make their brother reappear in the same way they meow at us when it's raining and they want to go outside!
I know the solution is to keep them both in at night which we often do anyway but I'm just curious whether anyone else has experienced something similar?