Should I keep in contact with my brother?

I lost my father about 6 weeks ago and was with him in the hospital tending to him the last few days when he was dieing of lung cancer, this was very emotional and shocking for me and I was very close to my dad having worked with him through the years too. I only have mum now as my close family, this has hit me very hard and i'm off work for a month for bereavement. My brother left the family when he was 16 to get married in about 1975, in all the time that has passed since then my brother has changed his surname to his wife's because she wanted him to and they have kept the three grandchildren from my mum and dad, (i haven't seen them either, but i feel the pain for my mum and dad) over the years my mum and dad have tried hard to make things right and have bent over backwards to bring them back into the fold on numerous occasions but my brothers wife is a very influential woman and has lied to my brother about trivial things to do with mum, dad and me, she has twisted conversations around so my brother has ended up saying there's no point in us all being "friends" to my mum and dad and not even listening to them, she has really tried hard herself in keeping him away from us and has succeeded, my mum and dad have never been nasty to her or about her. What with one thing and another it has ended up with my dad now gone and never having had his grandchildren in his life which i feel is so very sad. I wrote to my brother of my dads passing as mum and me felt it was only right , he came to the funeral and he said he wanted to come in person to say "I'm sorry too" to my dad, I really felt i'd liked to have said it's a bit late when he can't even hear you. my mum has now told me that over the years dad had really got used to the situation of never having grandchildren and doesn't want me to not have contact with my brother in case anything happens, I asked her what she meant as I thought she meant her, but she said what if something happens to him. Now my brother wants to keep in touch as if nothing has ever happened and has invited me to his home for a short stay if I want to get away from things for a break, I certainly don't want to do this but I feel that I would be betraying my dad by even chatting to him, and obviously none of us can go back now and change things, I don't really want to be in contact as hes denied my parents their grandchildren and i feel very strongly about this. I feel bad as a person as it doesn't seem "right" for me to be hard and not want to be in contact as he's supposed to be my brother, also i feel it may jeopardise him keeping in touch with my mum, who at 83 has only just started to come to terms with his not wanting them as parents and grandparents, this has gone on for 30 odd years with my mum torturing herself everyday for the way things have turned out, I have watched her live with hearing others talking of their grandchildren and knowing how hurt she is inside, my mum has sent cards over the years and phoned but my brother never really bothered with her or them as he just didn't want contact but mum never gave up. My mum and dad never did anything wrong it all just started with silly misunderstandings and lies from his then girlfriend and it just escalated, over the years my brother has soon known where to come when he needed money and has sent his wife on missions to us to get money from my mum and dad, which they have gladly given them to help them out with the children etc even when mum and dad didn't have much money themselves, but this has never ended with them being any more friendly, they have just kept away again. I just feel now my dad has gone it's a case of too little too late, and i feel my brother could be wanting to keep in touch in case my mum goes and he'll get money out of her estate. I don't feel he is keeping in touch to be nice to her as hes recently said two quite hurt full and unnecessary things to her on the phone about past things that his wife lied about, I feel this really isn't the time as she's just lost her husband and he can't even hold his tongue. i have had an e mail from my brother for 3 weeks now and i haven't answered it as i rather do nothing and silly enough i don't want to hurt his feelings when all the time i feel so strongly that he has denied my mum and dad their grand children over the years and made them very unhappy. i know this is very long but im so mixed up in my head as im still really grieving for my dad so I'd be very grate full for any-ones point of view on this to help me see more clearly. Thank you so much.