إِذْ قَالُواْ لَيُوسُفُ وَأَخُوهُ أَحَبُّ إِلَى أَبِينَا مِنَّا 

When they said:"Truly, Yusuf and his brother are dearer to our father than we..."

They swore, according to their false thoughts, that Yusuf and his brother Binyamin (Benjamin), Yusuf's full brother,
 
أَحَبُّ إِلَى أَبِينَا مِنَّا وَنَحْنُ عُصْبَةٌ

dearer to our father than we, while we are <b>`Usbah</b>.

meaning, a group.

Therefore, they thought, how can he love these two more than the group,
 
إِنَّ أَبَانَا لَفِي ضَلَلٍ مُّبِينٍ
 
 

Really, our father is in a plain error.

because he preferred them and loved them more than us