Sorry to hear this my brother passed away last year to lung cancer that spread to his bones he was told they didn't think they could get rid of it this time this was his 3rd time having cancer all I can say is make everyday count and be positive and fit as many happy memories in as you can my brother was my mums first born and only son she was distraught when he died and she still is now I've moved in with my children for the time being to give her company and a distraction my biggest regret was not talking to him enough and get a proper goodbye in my head I just didn't believe the cancer was going to beat him 

I'm so sorry to read this. I was in a similar position with my own brother (diagnosed with testicular cancer at 23) and my parents. My brother was also extremely strong. I feel the best support you can be, is to be there, be present, check in and offer your support, even if this isn't directly related to the situation. It's also important to take care of yourself. Unfortunately, there is no magic fix to make anyone in this situation feel better, maybe your support can make this journey a little easier day by day, whether that's just a quick chat on the phone or grabbing some shopping. 

I wish you and your family the best, my thoughts and prayers are with you.