Man... my first thought was Carnie and Wendy Wilson from Wilson Phillips, but they were the 90s, not the 70s and 80s. For the time period, I thought of The Pointer Sisters, but there were three of them, not two. Google reminded me of Ann and Nancy Wilson from Heart, and Crystal Gayle and Loretta Lynn, but none of them seem to have a house that fits the bill.
As for the illustrious previous resident, Marilyn Monroe lived in California, and Katharine and Audrey Hepburn both lived in the east.
Just thinking out loud, hoping it will give someone else a nudge...