Combined market share of mid-sized sedans made by Hyundai Motor Co. and its sister company Kia Motors Corp. ranked first in the United States last month, industry sources said Sunday. Sources said sales of Hyundai\'s popular Sonata sedan reached 22,754 units in May, while Kia sold 7,401 Optima sedans in the one month period. This pushed up market share of the two models to 19.0 percent of all mid-sized sedans sold in the U.S., surpassing GM\'s 18.8 percent.