Alva and Mary Ellen appear on the 1900 census in Eureka, Illinois with no children and on the 1910 census in Eureka with children (Al)meda, age 7 and Edna, age 1. In 1920, still in Eureka, “Metta” is age 17, Edna age 10, Hazel is 5, and Harold is 18 months. In 1930, still in Eureka, Harold, Hazel, and Rhodabell are listed. I don’t know where you are seeing half-siblings. All four censuses list the same parents in the same place.