Its really sweet of you to worry so much about his family like this. :)
I would talk to him and see how he feels first. Really listen to what he says and where his heart is going. In the end, you dont want to push him to do something he will regret. His mother needs him but his education is important too. He can pursue his Masters a bit later in life or closer to home but it will be hard to leave his mother behind when his father just passed away.
I would say talk to him and listen carefully to what he wants.
Good advice.