מִשְׁפַּ֤חַת בֵּית־לֵוִי֙ לְבָ֔ד וּנְשֵׁיהֶ֖ם לְבָ֑ד מִשְׁפַּ֤חַת הַשִּׁמְעִי֙ לְבָ֔ד וּנְשֵׁיהֶ֖ם לְבָֽד׃
The family of the house of Levi apart, and their wives apart; The family of the Shimeites apart, and their wives apart;
Rashi on Zechariah
the family of the Shimeites Shammua the son of David. Scripture first makes a generality about the house of David, and then it specifies each one.