What is the interpretation of the verse: "They said, 'If he steals, a brother of his has stolen before him'"?

Yusuf's brothers said when they found the king's drinking cup in their brother's baggage: (If he steals, a brother of his stole before), meaning that Benjamin followed his brother Yusuf in stealing. This was to absolve themselves, because Yusuf was not from their mother, and if he stole, it was due to the influence of his thieving brother's lineage. The exegetes differed regarding the type of theft they attributed to Yusuf, but these are unsubstantiated narrations. Al-Qurtubi commented that they lied against him in what they attributed to him.