Walburga Oesterreich (Dolly) married a wealthy man named Fred.  When she was 33, she was introduced to 17-year-old Otto Sanhuber, who worked at her husband's factory.  Dolly invited Otto to her home to "fix her sewing machine" and they began an affair.  Otto didn't really have any friends or family, so he agreed to move into Dolly's attic to make their affair easier.  During a fight one night, Otto flew out of the attic and murdered Dolly's husband.  She began dating other men and kept Otto in the attic to be her sex slave and she told people he was her vagabond half-brother.

Website: https://www.drinkingthecoolaid.com/ 

Resources:
The La Brea Tar Pits Mystery | The Institute for Creation Research (icr.org)

The Story Of Dolly Oesterreich, The Woman Who Kept Her Secret Lover In The Attic (allthatsinteresting.com)

Walburga Oesterreich | Murderpedia, the encyclopedia of murderers

Watch A Crime to Remember Season 4 | Prime Video (amazon.com)