Presuming from your question that your brother is a U.S. Citizen, he will be able to petition for his parents in the Family-Based Immediate Relative category notwithstanding that he has had two DUI convictions. Absence of a criminal arrest/conviction record for a U.S. Citizen is not a qualifying criterion for ability to sponsor a parent, although if the U.S. citizen is in prison or otherwise unable to demonstrate sufficient earnings he may need to find another Citizen or Lawful Permanent Resident ("Green Card" holder) to serve as a joint sponsor.
If you brother is the US citizen petitioning for his parents, it will have almost no effect on the process because the concern is the criminal history of the intending immigrants.
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