What can I say to comfort my boyfriend?

My boyfriend and I live here in the us, his son lives with his ex in central america. She told him how his son is very sick and his health is deteriorating super fast. Obviously, my boyfriend feels sad and is depressed because there's nothing he can do at the moment. The thing is, I have never been good at consoling other people- I never know what to say and usually stay awkwardly quiet. But I don't want that to be the case now. What can I possibly say to my boyfriend so he can feel a little better?