the Parole Board can revoke a parole merely on an arrest. it does not need a conviction - the Parole Board's standard is a preponderance of the evidence - not like in a court room where there has to be a standard of proof which is beyond a reasonable doubt.
so, i just want you to be aware that the Parole Board does not need a conviction. it can revoke simply on a charge.
however, with that being said, if he has done well while on parole, as i discussed earlier, and he is not convicted then the Board may continue him on his parole. additionally, when the Board revokes they are dealing with a "liberty interest" - that means that while there is no right to parole once the Board has granted Parole, they need a good and substantial reason to revoke it. in other words it cannot be arbitrary or capriciously
therefore, should his parole be revoked he does have a right to appeal it to the courts.
the botXXXXX XXXXXne is - it's 6 of one and 1/2 dozen of the other. if you can get a lawyer who can get the DUI dismissed that may carry weight with the Board - although it does not have to because as i explained the Board does not need a conviction
if you hire a lawyer to handle the revocation hearing they may be able to present your brother in such a good light, with employment references, community ties, good compliance with the Parole Officer that the Board would not revoke on a mere arrest.
perhaps, now that i have explained it all to you, you might consider a consult with a local attorney to discuss both the DUI and the Parole revo hearing. maybe you can get a lawyer who will handle both for a flat fee.
if you need a referral for an attorney i suggest you contact the CA Bar Association - here is that information
please follow up here, if you still have more questions on this matter.