Genesis 13:8

for we are brethren i.e. kinsmen; Abram being Lot's uncle. Cf. Genesis 14:14, "and when Abram heard that his brother (i.e. Lot) was taken captive."

Abram, as the elder, takes the lead in the conference: his proposal is made with generosity and dignity. Lot, though the younger, is to have his choice.