Modal verbs of probability are used to express an opinion of the speaker based on information that the speaker has. Example: He must be at work, it's 10 o'clock. In this case, the speaker is 100 % sure that the...
Gee, I don't agree with all of his choices. I would say "They might be living in New York" to express a situation in the present that I was unsure of. "They could live in New York" expresses a future possibility.
Modal Verbs of Probability 
Linear Mode
