Well Keturah was NOT born a Rossiter she married a Rossiter. She was born Keturah Walker. There is no problem with the birth of Olive Frances - she was registered in Hackney 1902. Her parents were Frank and Keturah Rossiter. Surely if you purchased the marriage for Olive it would show her correct father and maybe other helpful details as well. Rossiter is not my direct line, but as I am helping a cousin I do have a lot of info on them. What else do you need to know.