Just woke up from a dream. I was a little kid, in a room alone,

I was sitting in my room when I was eight playing with legos with my older brother.

An older woman came into the room and sat down on his bed and asked us if we've been good boys.

We said yes.
Then we asked her how she got here, and if mom let her in. We didn't know we had a new grandma, and when we looked back at the bed she was gone.

My brother brings this up with me every now and then, like he still can't quite believe what happened.

I don't have any spooky stories to share OP, but in my honest opinion, your story was very... Boring not scary or whatever in the slightest, but that's just my two cents.