Why did Eliezer say "the house of my master's brothers"? Besu'el was Avraham's nephew!
Moshav Zekenim: He wanted to her to hear this and tell her father, so her father would think that his brother came with great wealth, and go out to greet him. 1
Redak: Besu'el was from Avraham's brothers, Nachor, and Haran (Milkah's mother). When he spoke to her family (Pasuk 48), he said "of my master's brother" (singular).
It is not clear why it was permitted to mislead him (PF).