You should consult with an experienced immigration attorney as soon as possible.
You should consult with an experienced immigration attorney, whether myself or one of my colleagues, to thoroughly review your situation. Nothing in this post should be considered legal advice and no attorney-client relationship has been established.
Your brother has gotten himself in a difficult situation. A drug-related felony is classified as a "crime of moral turpitude" which has a lengthy "bar". Marriage will not likely overcome the consequences of a CMT, especially under the circumstances you describe. Waiver not likely. Consult an experienced immigration lawyer for options.
The challenge is whether he can file for adjustment and if a waiver of inadmissibility can be granted as a matter of discretion. If he entered without inspection, then he must prove that he was somehow admitted and inspected or qualifies for what is called Section 245i relief.
If these have yet to be discussed, then we likely have concerns. A petition will need to have been filed by April 30, 2001 for him or his parents. There may be other issues, as well. This seems possible, even if unlikely.
If he somehow gets married, while in custody, our concern is whether he will have to eventually try to process outside the U.S., which can prove extremely difficult based upon his conviction. If he has an aggravated felony, most Immigration courts won't wait for the spouses I-130 petition to be approved. He cannot get bonded out of immigratoin detention if he was convicted of the drug distribution. Good luck.
This is general information, not legal advice, and does not create an attorney client relationship.