Complex sentence: He remained head of the house until 1966 when he had abdicated as head the house in favour of his son Prince Ferdinand Maria, he died on the 13 January 1973 in La Combe.
Split into simpler sentences: He remained head of the house until 1966 when he had abdicated as head the house in favour of his son Prince Ferdinand Maria. He died on the 13 January 1973 in La Combe.