My healthy dad fell into a deep sleep while standing up. Should I be worried?

[kegrmc]

My dad is a white, male, 58 year old and is around 6'3 and 190 lbs. He is in good shape (plays tennis a few times a week). He has no existing or past medical conditions and is not on any medication. All of my family has low blood pressure, especially him. It was around 1am when I walked inside my parents house (I am a college student who has just gotten home for Thanksgiving break). My dad had been asleep for the past hour or so on the couch, but when I walked in he had just gotten up and was grabbing a few cups to take in to the kitchen. I started to tell him about a show I started tonight, and I could tell he was very sleep and still in a dreamy state because he only said a word or two in response. I then asked him a question about something and he didn't respond. At this point he was around the corner so I couldn't see him and figured he must be reading a text. After about 5-10 seconds of no response, he stumbled into view and was very off balance spilling his drink and I could tell he was about to fall over so I ran over and grabbed him. I thought he must have been extremely drunk, but I found this very odd because he never has more than a few beers/drinks. So I grabbed him and started asking if he was okay and then he passed out completely. I got him to the ground and rested him against the wall, all the while he was snoring and in an extremely deep sleep state. I was yelling "Dad" and shaking him to try to get him to wake up and finally after about a minute (this is an estimate since my adrenaline was at an all time high) had elapsed since he started stumbling, he woke up and was very confused. It started to come back to him. At this point my mother and sister had both ran down stairs and I had told them to call 911 but by the time they grabbed the phone, my dad had fully awaken and was saying he felt perfectly fine, just that he was super tired. So he lied on the ground for a little and I made sure he didn't feel any pain in his heart or any differences at all and he assured me multiple times that he was perfectly fine and that he had just passed out from standing up so quickly and from being sleepy. To make the situation even worse, my mom feinted from the shock because she thought her husband had died. I knew he was alive and sleeping the whole time since I was holding him in my arms and could feel him, so I calmed down my mom and my dad assured us we did not need to worry nor call 911. My dad, mom, sister, and I all have a history of feinting, although I have never seen someone fall asleep while standing up. My father is the type of person who always believes he doesn't have anything wrong with him and will 100% refuse to see a doctor. Is this something we should make him get a brain or heart scan for? Or is this somewhat normal, and definitely the result of him being both lightheaded from standing up and very tired/dreamy? Also, he was awake and answering questions completely normally once he woke up, and he is also a very deep sleeper when sleeping normally.
This was all very disturbing for me (and the rest of my family) and we would all love to get some peace of mind.
Any help is extremely appreciated. Thank you for taking the time to read this and I hope it's all very clear. If I need to provide any more information please ask. Thanks

[TheLightSeeker]

If this would happen to him while driving, he would be putting himself, his passengers and the general public in great danger.
Now if this does not convince him to get tested, IDK what will.
The family history of fainting is truly puzzling.
A genetic connection with one parent and 2 children extremely rare but possible.
Now both parents and  2 children, impossible(only mathematically possible,) so everything points to external, environmental , or non-genetic causes.
The only common  factor mentioned in your post is low blood pressure. Again rare involving all 4 members of a family!
You all need to play detective to figure out what this might be.  Low salt  diet, carbon monoxide in the house...?

And consider all of you getting evaluated for both the low blood pressure and the fainting.

It's a wise choice, to my opinion, for your long-term health, safety and other peoples safety as well.

Best wishes,
Niko