My son, the youngest of 4 (three older sisters) is 21. As a somewhat ADHD kid with some minor learning differences, his effective age has always been 3-4 years behind his chronological age, so he's more of a teen, emotionally.
He is home for the semester, as he struggled with some health and academic issues this winter, and he'll return to college in the Fall.
Meanwhile, he doesn't see his dad often. I try to take him in with me every couple of months, most recently yesterday. Gabe (my son,) was there briefly, then went out to the lobby to visit the ALF dog instead.
His dad is, at this point, nearly catatonic and I really perceived--maybe more acutely than I have in the past, when his dad could interact at least a little--how difficult this is for him. Gabe was a very young, pre-adolescent boy when his dad began to have symptoms, and he says that he doesn't really remember his dad as a fully functioning person.
Gabe will have to process this as he matures. I can see that this is something that he partly copes with by just not thinking about it, and it doesn't feel like a kindness to make him face the situation more than he must.
The girls--now 23, 24, and 26--have always been more mature emotionally, and have, for the most part, been able to face what's happening and become caregiving when they are with their dad.
Gabe is a funny kid who enjoys imagining fantasy scenarios. Whenever he sees his dad, we leave and he invents a fantastical way in which Alzheimer's either doesn't exist or is curable.
Emily = boys more often than girls can detach from emotions. My brother just a year older has no memory of my dad beating me as we grew up even though he was right there or how mean he was to me. A counselor told me this is quite common for boys. When our mom was sick with dementia and other problems he seemed to never be upset or affected by it. To this day he has never shown emotion over it. When his wife was diagnosed with breast cancer - twice - neither time did he get emotional over it.
You son may be doing this too. Fantasy may be his way to cope with his dad's illness. I would just let him have it for now as sounds like he has other more important issues of his own to deal/cope with.
Emily, my heart aches for all your kids--and especially Gabe. It reminds me of what Steve went through with his Dad's AD. He was maybe 11 when the symptoms first became noticeable and about Gabe's age when his Dad passed. Someone told me he didn't cry when his father died, and Steve told me many times "I never really had a father." It was rough, but with a strong mother and the help of the extended family, Steve became an exceptionally caring and loving person as an adult. I never saw evidence that the experience scarred him in any negative way. I hope knowing that may help with any worries you have for Gabe's future.
Our youngest (17) DD says she does not remember her dad any other way than with AZ. Sad that they grow up that way. She spends a lot of time away from the house, and I let her. It is not normal to have to care for your parent. She is always willing to help me when needed and I am so glad to have her here with me. But I let her get out into the normal world when possible.
Just give Gabe time. He will come to terms with all of this as he matures.
I do feel so badly for the young children. Lynn and I both had a key role in helping to raise my niece and nephew whom live with us. I have shared here before how difficult it has been for them. Having it be your true parent must be even more devastating. I think moments of fantasy is a healthy way to try to escape the harsh reality.