Complex sentence: Needham was the only child of a London family: his father was a Scottish doctor and his mother, Alicia Adelaïde Montgomery (1863--1945) was a French-Irish composer and music teacher.
Split into simpler sentences: Needham was the only child of a London family. His father was a Scottish doctor and his mother, Alicia Adelaïde Montgomery (1863--1945), was a French-Irish composer and music teacher.