Obliged to make a home away from home in America, Moon Shadow's survival and adaptability depends not only on his father but on the friends that they make along the way. As we come to see with the men of the Company and the Whitlaws, Moon Shadow's friends are his family in America. The significance of friendship throughout Dragonwings expands our common understanding of family to expand across blood lines.
Since friends are people who support you no matter what, Mother is Windrider's best friend in Dragonwings.
Since friends are people who know what you need better than you do, Uncle Bright Star is the best friend to Windrider in Dragonwings.