My sincerest condolences Bigbuck.
I too recently lost my last Grandfather (93), it happened way too fast!
I do however still have one Grandmother left (recently widowed after 73 years of marriage) and I was visiting with her this morning ( I try to do it weekly, or more) and it's always a good time.
At 99 he's a very fortunate man as are you to have had him in your life for so long. May his memory always be a part of you, God bless.