My father cries a lot. We are at a loss what to do.

When my father had a "mini" stroke for the 2nd time late March 2019 (1st one 10 yrs prior) the Dr. only ordered blood/urine tests, head CT & a NeuroPsych eval. The blood/urine/CT results were all normal. The NeuroPsych eval took 7 months to get in. He was diagnosed in Oct. 2019 "Isolated Memory Impairment vs. Mild Dementia, suggestive cerebral vascular basis for cognitive difficulties, poss. lateralized to the left hemisphere." When we followed up with his PCP, I was given a copy of the report, and we were told to come back in 6 months. No referral to Neurology was suggested. I did request a referral to U of Mich. PT Department's "Drive Ability" program and his driver's license was eventually taken away. He was very angry for a few years about losing his license and eventually his PCP agreed that we could try an anti-depressant. He's on Cymbalta now 60mg. Not much changed and life became day to day.
I moved in with my parents late March 2019 after his "stroke" when I discovered that Dad wasn't paying some of their bills and putting salt in the water softener, etc. VERY unlike him.
My mother also was not formally diagnosed with Alzheimer's, but her brother died from it and her sister was diagnosed has been in a memory care facility since 2018. Mom also had no memory and was on dialysis. I eventually learned how to do her dialysis at home and what foods to avoid etc. Dialysis was her last contact with other people/social life and I was very sad when she gave up driving herself back and forth to dialysis, but was happy I was trained and could treat her at home.
They kept me very busy, despite their routines were simply to get out of bed each day, spend the day in their recliners and back to bed each night. The TV always on. News for Mom & NCIS for Dad. Dad didn't keep in touch with any of his friends after retiring from Detroit Edison in 2003. It was pretty much, just the 2 of them. Neither of them were very social.
Last year Mom fell, hit her head, brain bleed caused her to lose the ability to swallow, we had Hospice get her out of the hospital, to be home with Dad and she passed 2/25/24
They had been married since 1956. Held hands while they slept at night.
Here we are shy one day of Mom's passing a year ago. Dad's cognitive abilities have continued to decline. He can't change the batteries on his TV remote anymore or use a phone. It's too confusing.
The past 6 months it seems like he is more aware of his mental decline and lack of memory and it makes him very sad. He has reached the point where he is sobbing almost every day now.
I am on a 6 week break from care giving and my sister Julie is staying with Dad while juggling a full time job after moving her computer from home. We are at a loss with how/if to console him.
At first I/we would run to him, hug him and tell him we missed Mom too. We would cry and look at photos or reminisce together and eventually I could coax him to come have breakfast or lunch. Then it seemed like I should maybe let him occasionally cry on his own thinking we all need to grieve in our own way sometimes.
Mom was my best friend. My husband & I traveled many times with my parents. We have lots of good memories.
His 87th birthday was 2/20. He spent the day in his recliner in front of the TV. Julie had to wake him up to eat lunch and handed him the phone when his older sister called to wish him a Happy Birthday.
He fell back to sleep after lunch. When Julie brought him dinner she mentioned how nice it was that his sister called and that she made him a special dessert for his Bday supper. He couldn't remember the phone call. He wouldn't eat. Kept asking things like "when did she call?" "I had lunch?" and started crying. Julie tried to answer his questions until she decided to call his sister back so that he could talk to her again. Eventually he stopped crying.
He sobbed for a good half hour this morning before getting out of bed. Our hearts are breaking.
We are wondering if anyone has any suggestions for us and very thankful for this support group!