Joseph. "The fruitful vine" (Gen_49:22) has two tribes (not merely "families"). Thus Joseph has "the double portion" (1Ch_5:1, 1Ch_5:2).
Ephraim. Blessed first (Gen_48:19, Gen_48:20), is here named first, and is increased more than Manasseh (Deu_33:17). But in journeyings his numbers were diminished by 8,000. See Num_26:37, and compare 1Ch_7:20-22.