Complex sentence: Mr. Biggar's sister Marie Eliza, married Herbert Charles Wilson who served in the legislative assembly for the Northwest Territories while Mr. Biggar's grandson, Oliver Mowat Biggar served as Canada's first Chief Electoral Officer.
Split into simpler sentences: Mr. Biggar's sister Marie Eliza, married Herbert Charles Wilson who served in the legislative assembly for the Northwest Territories. His grandson, Oliver Mowat Biggar served as Canada's first Chief Electoral Officer.