Location: Main Castle, randomized
Rescue Reward: Master key
From the Manual: Lord Belmore is a London barrister and legal council to your father for years. He has been asked to join the family to Romania to witness and take care of the legal aspects of the marriage.
While most of your relatives greet you with expressions of thanks and encouragement, Lord Belmore threatens to sue you if you don't save him. When faced with danger, he nervously screams out "A dead lawyer is a bad lawyer! A dead lawyer is a bad lawyer! Nyah!".
Lord Belmore appears randomly inside one of the small dead-end rooms in the corners of the Main Castle. You can recognize these rooms as they usually contain a lesser vampire coffin, and if Lord Belmore doesn't appear in them, a Gargoyle will appear in his place. Saving him will reward you with a Master Key that opens all your family trunks, letting you get at all the special items even if you let a few of your relatives die.
TIP: Because the Main Castle is such a pain, you probably don't want to search all 5 floors for this Lord Belmore. Instead, find one of the rooms he may appear in, save outside, and keep going in and reloading the save until he actually does appear.
BE CAREFUL! As soon as the 14th family member is saved or dead, the game will automatically skip to 6:00 a.m. for the final battle. The 15th family member will automatically die when this happens. Since your Father and Lord Belmore are normally the last two relatives, rescuing one will usually kill the other. The only way to save them both is to locate both of them inside the Main Castle and bring them to the Sanctuary at the same time. The best way to do this is to find your father, then go to one of the rooms on the 1st or 2nd floor where Lord Belmore may appear, quicksave outside, go in, and keep reloading your quicksave until Belmore appears inside.