Complex sentence: After his death, Frederick's family left Cliveden and the estate was once again used by Orkney's heirs until the night of 20 May 1795 when the house caught fire and burned down.
Split into simpler sentences: After his death, Frederick's family left Cliveden, and the estate was used by the Orkney family until 1795. On the night of 20 May 1795, the house caught fire and burned down.