For example would there be bilingual Chinese and Korean speaking communities living in the same city? Did Chinese/Korean marriages ever happen?
In what time period? As I said in another comment that you seem to have ignored, please write more to your questions. This and many others don't really give enough to go on. You need to specify a time. It's not really possible to give you a good answer with the way this and many of your recent questions are phrased.
There are a lot of good answers to all these questions that you're asking in rapid succession but you're not going to get those answers if you don't ask in a way that helps the answerer.