Complex sentence: She would then introduce him to her daughter, Eily Gertrude Shaw (1888 --?), whom he fell in love with, producing a number of portraits of Eily, before marrying her on 4 September 1911.
Split into simpler sentences: She would then introduce him to her daughter, Eily Gertrude Shaw (1888 --?), whom he would enter into a relationship with. Falling in love with her, Spare produced a number of portraits of Eily, before marrying her on 4 September 1911.