Complex sentence: From 1866 until 1874 he ran John Conolly's private asylum Lawn House in Hanwell, marrying Conolly's youngest daughter Ann, who was by then 36 years of age.
Split into simpler sentences: From 1866 until 1874 he ran John Conolly's private asylum Lawn House in Hanwell. He married Conolly's youngest daughter, Ann, who was by then 36 years of age.