He is still Grandpa.
He is still Step-Dad.
Just because your Mom may not be around, that does not make the person "disposable" and non-existent.
You say he is a great guy.
That is the bottom line.
He will ALSO be mourning your Mom. Men... mourn differently. So allow him that.
He IS, "family." He is your Mom's Husband. They have been married a long time. The kids call him Grandpa and know him as Grandpa.
He is.
HE probably feels uncomfortable TOO. And does not intrude on you all, because he knows he is a "Step" Dad. So he is trying to respect "boundaries" instead of being a pushy man.
Put yourself in his, shoes.
It is about time, after being married to your Mom for FIFTEEN YEARS... that he is made to feel welcome and at home with you all.
He probably feels like an outsider.
But is and wants to be, a part of the family....
Now, just to share something with you: My Dad died about 11 years ago. Once he died... my Dad's family pretty much.... IGNORED my Mom and NEVER EVER contact her anymore. At all. Because, she is an "in-law" and since my Dad died, they make NO EFFORT AT ALL... to still make her a part of the family. It is HURTFUL. To her and us. Those are our cousins, too. It is very... cold and callous and so lacking in emotions.
ONLY 1 cousin, and 1 Aunty from my Dad's side of the family, will contact my Mom. About a couple of times a year. BUT... my Mom, on her own volition, TRIES to contact them and make conversations and calls them. They are not always, so friendly. Not, since my Dad died.
-And it shows their true character... and how they all these years, must have just not given a damn about my Mom as an in-law or as my Dad's Wife.
So please think about that... side of the coin too.
Think about how you all... think of your Step-Dad... presently and later... and how it might feel for him. That he is perhaps, regarded as not 'really' family. Just because he is the Step-Dad and 2nd Husband and "not blood" family. To you all.
I am sure... he thinks about this too... and it may be a sensitive thing for him too.
AND... I am sure... he is thinking about what his life will be.... when/if your Mom passes on. How will all of you... regard him... afterward?
Again, he is family. He is "Grandpa" and he has been for the past FIFTEEN years... of your Mom's life and your lives.
He is not a 'friend.' He is... family.
And yes, you still include him or visit him at Christmas.
And yes, he is STILL Step-Dad and part of the family.
And yes, if he re-marries, respect that.
And YES, you talk to him... before your Mom passes on. And do not assume... that you all and he are just "passing" seasons to each other and just move on when/if your Mom dies.
Again, all I know is how it feels, when 1 side of the family, pretty much IGNORES you/your family, after 1 member of that family dies.
My Dad's family, makes NO effort, to even stay connected with my Mom or us... since he died. That pretty much means, they don't care. And are just really, shallow. It is, hurtful.
You are all grown-ups now. Not kids.
Your Mom re-married and has been married to your Step-Dad for 15 years.
It is time, he is thought of as family.
You said he is a nice man. And if your Mom was happy with him, then respect him for being a happy part of your Mom's life.
It is not only his job... to "integrate" with you all. It is your job, too.
For him, and for your Mom.
Your Mom... most probably WORRIES about him too... and how you all, will react toward him, after she passes.
That is a huge thing, to have on someone's shoulders, when they are ill and they are not going to live much longer.
My Dad was ill... before he died. He worried about us and our Mom. His Wife. That is only, natural.
Show your Step-Dad, that he IS 'family' too. After all these years.
And mean it.
So that your Mom does not have to worry, about him and his being alone, without her.
That he will STILL have, family. Too.
Yours.