I have had dreams like this - the latest one really, really blew me away.
I am NC with the paternal side of my family. All of them. The vast majority aren't very nice people, very narcisstic and on the advice of a therapist I cut them off. Unfortunately, whilst the majority are utterly vile, there are a few that aren't and my Nana was one of them. I missed her so much but if I contacted her they would have made her life hell and she was a bag of nerves as it was. I didn't want to put her in that position, she was an old lady.
Her husband, my grandad, died a few years ago and I had to hide in the balcony of the church to watch the funeral service. I loved him, too, although some of his behaviours weren't the best, he was a good grandad to me.
Anyway, it's been around 5 years since I last seen or heard from any of them. When I say NC, I mean completely no contact - any attempts to provoke a reaction from me (such as FB posts) have been ignored and I've had absolutely no insight into their lives in that time.
A few months ago I had a very, very vivid dream that they both came to me to tell me nan had passed, that they wanted to take the family's power away and tell me themselves and that they love me very much. I woke up and said to my husband "I've just had the most vivid dream that my nan has died". I genuinely just thought it was a dream at that point, albeit a very very vivid one.
Fast forward to 10:30 that night and a cousin of mine, who is also no contact with them, called me to tell me nan had died after my dad text her dad to inform him. When she asked if I was busy and could she call me before she even said yes I said "has Nan died?". I just knew. Only the fact that I'd spoke out to my husband that morning about the dream I'd had, you just wouldn't believe it.
I found a lot of comfort in it but the accuracy did spook me. I didn't attend her funeral as I felt like I could say my goodbye in private and had closure from the dream.
So yes, I think these dreams have some weight to them, but it's hard to decipher without evidence if that makes sense? For example, my dream was confirmed to be a reality later that day, but you don't have someone who found a body (yet!) so could be written off by people (I personally think there's something in it)