I've debated on whether to say anything or not on this. I've gone through a horrible 5 years with both parents having different types of dementia. I've guilted myself into wondering how I could have missed the signs and what can I do to help others, as early diagnosis and treatment helps delay it.
I'm not a neurologist, and it does require a very lengthy trip to one to get the diagnosis. Memory issues can also be related to other things going on, or medication being taken to treat those other issues. However, going off my experience with what I saw with my dad, their dad is showing the same signs. Now, is there a chance their dad has always been a bit absent minded? Sure, we never knew him before he started making appearances with Jenna and Josh, but to me he's gone downhill since then.
IMHO, dementia is one of the cruelest diseases. The notion that the patient is unaware of what is going on is entirely wrong. They know, and it rips them apart as they don't understand why they're feeling lost.
When these issues are noticed the KIDS are the ones who MUST step up and force the parents to the physician. They MUST be the ones to sit in the car and assess their parent's driving skills and take the keys away when they're not seeing the road, pedestrians, lights, or getting too distracted. It's impossibly hard, but it saves lives.
JOSH and JENNA MUST STEP UP and start caring. They're depending on a long, good history of their parents always being there and not looking at the future which may be right around the corner. IMHO, Dale shows the most caring out of the younger generation. Steph is too wrapped up in her own existance and kid. Josh's caring is out on Mars and Jenna flits between being a child and an adult, whichever suits her needs best.