Complex sentence: Although he and his wife had no children of their own, in 1821 they took responsibility for three nephews and a niece when the four children were orphaned; at the time, Watkin Tench was 63 and his wife was 56.
Split into simpler sentences: Although he and his wife had no children of their own, in 1821 they took responsibility for three nephews and a niece when the four children were orphaned. At the time, Watkin Tench was 63 and his wife was 56.