Complex sentence: Of his siblings, oldest brother Ralph was the most advanced musically, proficient on the violin, while his sister Laurine had the strongest connection with Aaron, giving him his first piano lessons, promoting his musical education, and supporting him in his musical career.
Split into simpler sentences: Of his siblings, oldest brother Ralph was the most advanced musically, proficient on the violin. His sister Laurine had the strongest connection with Aaron, giving him his first piano lessons, promoting his musical education, and supporting him in his musical career.