Complex sentence: Austin's mother, Eliza Osman, was the daughter of a Royal Marine and had been born in Devon, before marrying Philip Spare at St Bride's Church in Fleet Street in December 1879.
Split into simpler sentences: Austin's mother, Eliza Osman, was the daughter of a Royal Marine and was born in Devon. She married Philip Spare at St Bride's Church in Fleet Street in December 1879.