Winnie,
I trust that you and Chi On hv both tried your best ~ you have done everything you can to find ways of treating the disease. We do not understand God's ways. May He wipe away your/Fei Fei tears and give you/Fei Fei strength and courage to continue life's journey knowing that Chi On is cheering you/Fei Fei on in spirit.
He will be awaiting at heaven's gate for the big reunion at the end of your journey! Until then, trust that God's grace is sufficient to carry you/Fei Fei through...Psalm 18:6