Hello punkrockmama and welcome to the forum. I have had this problem before, and while I was able to fix it, this fix has not worked for everyone. Here's what I did, step-by-step. I went to the Edit Town screen and I clicked on the family. I then clicked the Copy to Library button and then clicked the option to copy them with the house. Once they were safely in the library, I deleted the bugged family and house. Then I placed the copy back onto the same empty lot. I hope this works for you!