COMMENTARY on 12:11
A. Yusuf Ali:

Translation:
They said: "O our father! why do you not trust us with Joseph,- seeing we are indeed his sincere wellwishers? 1642
Commentary:

1642  The plot having been formed, the brethren proceed to put it into execution. Jacob, knowing the situation, did not ordinarily trust his beloved Joseph with the brethren. The latter therefore remonstrate and feign brotherly affection.