If I recall correctly, this mansion was designed by a man with the same surname. He and his family likely lived in the area during construction, and when he outlived his usefulness, they all made perfect playthings.

[ But that was just a theory. He couldn't be sure without snooping into records, and he didn't care enough about the mansion or the girl to waste his time with it. ]

Umbrella and those behind it certainly aren't the types to have any qualms about taking out entire families.