Why did not Marty Robbins bio mention his twin sister Minnie Minotto?

Marty Robbins' biography may not mention his twin sister Minnie Minotto due to a focus on his musical career and public persona, which often overshadows personal details. Additionally, Minnie's life may not have been as prominent or relevant to Robbins' story, leading biographers to prioritize other aspects of his life. It's also possible that the information simply wasn't widely documented or known.