I totally sympathise whoisthis I really do.
My dad looked after my late mum for many years as she had bone cancer and kidney failure. She was a dialysis patient for several years and he accompanied her to almost every one of her 3 times a week sessions! they were virtually inseparable and both made many friends on the kidney unit.
After quite a long spell in hospital where she was very poorly she decided enough was enough and discontinued the dialysis and asked to come home to die, where she passed away peacefully a week later.
Moving on 3 years, my dad has (very reluctantly at first) forged a new life for himself. He is 81 and has started meeting some old friends 2-3 times a week. He is going to his football again and is enjoying life. He relies on me a lot for hospital appointments, shopping etc. and we include him in everything we do as a family, but generally he is doing much better than either he or we thought he would. He has always been good at cooking, cleaning etc. as my mum couldn't do much for a very long time, so his little bungalow is like a new pin and would put a lot of younger, more able people to shame!
He still talks about my mum constantly but it seems to have gotten easier of late and we are able to share our happy memories of her without getting upset.
I agree with what Maw has said, you must convince him that you will always be there for him and not just in the beginning of life without his dear wife.
It will get easier for him it really will, but you mustn't let him give up. He has to find something to occupy his days.
Wishing you and your parents my very best wishes. x