"My extended family used to live in an ancient house located just north of London. Previously, it used to be Queen Victoria's stop when she was traveling in the area.
I'm told when my uncle (mum's sister's husband) was younger, he never believed in ghosts or spirits and would be the first one to call it a load of rubbish. He was sleeping one night and was awoken by a man staring at him at the end of his bed, dressed in an old army uniform. My uncle froze for a few seconds, panicked, and flicked the bedside lamp on and then the man vanished.
He refused to sleep in that room from that night onwards.
We later found out that the man was a previous owner who had returned from the war to find his wife having an affair. He was so furious that his wife reported having told her he would do the worst thing possible to get back at her.
He took his twin sons (toddlers at the time), went to the back of the garden where there was a forest, and shot them both dead before killing himself.
The funny thing is that since my family bought the property, my uncle had twin sons, my mum had twin sons and my uncle's brother (who is also a part-owner of the property) had twin sons.
The weirder part is that my brothers and my uncle/aunties kids were playing near the forest when they were in their early teens and kept on saying they heard boys laughing but couldn't see anybody there (not knowing the house's history)."