I saw just snippets of this horror movie about ten years ago. I believe it was in black and white and it may be from the UK.
The scene I remember is of two adults (who are ghosts) and they are brother and sister. Their mother killed them in a fire after she discovered they were involved in an incestuous relationship.
I do not think the movie was as much horror, as suspense.
Could it be Haunted (1995)? This is not B&W but the other things that you mention match.
After reading the description of “Haunted,” I believe you are right! Thank you!
Our first official movie solved by a registered user! I can finally try out the leaderboard. đŸ™‚