Is med school just a back-up plan for him because he can't get a job as a ChemE? If so, he will most likely be disappointed.
First off, his grades are a huge strike against him. It is passed along throughout the pre-med community that you get a little bit of a break in regards to your GPA if you were an engineering major because of the amount/difficulty of classes you took compared with the history major. However, a 2.8 in ChemE looks infinitely worse than the History major with a 3.9; all they have to weed people out is numbers. There are tens of thousands of applications to med schol every year, most of them with much higher GPAs and a lot of volunteering (I've heard the average now is around 3 years of volunteer ECs for the incoming matriculant).
In addition to all this, schools use a computer to screen out certain applicants, to decrease volume some. 3.0 is the bare minimum to even get your application read by a human being. Of course, having someone look at your application is far from a guarantee of even getting a secondary.
Let's say he was lucky enough to get an interview. Does he really want to be a doctor? Will he be utterly depressed and live a life he feels is unfulfilling if he doesn't get into medicine? Medicine is a tough route to go, and unless your bro is 100% sincere in his desire to be a physician, the interviewers will see right through him.
So now let's look at it from a logistical standpoint. He has a 2.83 GPA with roughly 128 credits, I'm guessing? If he took 30 credits and achieved a 4.0 average, he is still looking at roughly a 3.05 cGPA. It's impressive to get a 4.0 for two semesters, but not uncommon in the pre-med community. Upward trends in grades are considered, but with 4 years of poor grades, it will take at least 2 years with a GPA of as close to a 4.0 as possible. He must also take the MCAT and get a very good score, because his GPA can't compensate for a below average score.
His best chance, if he chose to take a couple of years of classes to get that magic 3.0 average, he would probably not get in anywhere (except possible a couple of osteopathic schools, which are more friendly towards non-traditional students), in which case he should apply to an SMP program. SMP stands for Special Master's Program. An SMP is an intensive one-year MS (non-thesis) degree where you take courses in a medical school, and are graded just like a medical student (i.e. in direct competition with them for class rank). If you get a high GPA (> 3.5), you have a decent shot at getting accepted somewhere. Georgetown and Tulane are a couple of schools that offer SMPs. They are very expensive; around 30 grand. They are also worthless if you don't get into medical school, because all you learned was the first year of basic sciences (biochem, pharmacology, maybe public health). The worst part is, even if you do get into a med school after the SMP, you have to retake the first year classes all over again (that's right, there is no exemption for prior courses in medical school, at least at most places).
So length of schooling is now at a grand total of:
4 years of undergrad
2 years post-bac UG to get the 3.0 necessary to apply to med-school/SMP (I forgot to add that you need a 3.0 and an MCAT score of around 30 to get into an SMP. 30 is the avg score of an accepted student to med school, BTW)
1 year SMP - after this, hopefully he is an M1
4 years of medical school
Now he chooses a specialty; let's say he goes for the shortest route possible, Family Medicine
3 years of residency (>80 hours per week, on-call duty, periods of 36 hours on a shift over the course of two days; resident pay floats around 50 grand/year. Yes, that's correct, guys. A resident averages about $12/hour)
So 10 years from NOW, he would ideally be a Family doctor; and be a little over $250,000 in debt, in all likelihood (probably more, after interest has accrued). Factor in that a Family doctor only makes around $150/year. Specialties that pay well, like the ROAD specialties (Radiology, Ophthalmology, Anaesthesiology, Dermatology) are extremely difficult to place into (save for gas, which is not that difficult at this time).
Sorry to be a buzzkill, but as a pre-med, I think it's only fair to warn others who seem like they may not have totally though this out beforehand. Medicine has an enormous amount of really bad aspects, like the things I mentioned above. It's a tough road, takes an insane amount of work, sacrifice, and committment. This is why I say only take this road if you honestly feel you could not live your life doing another profession. The pay isn't that great if you factor in loan repayment, malpractice insurance, and quality of life (hours you work, on-call schedule). Hell, a lot of doctors tell us pre-meds to get out of this game before it's too late. Universal healthcare is also a big concern to a lot of physicians.
Has your brother considered medical physics? His GPA is low, but if he could boost his GPA a little, he could probably get into a 2-year Master's program somewhere. That's 2 years of schooling, a noble job (rad. therapy), and a very nice salary. I think med. physicists with a MS and certification (take some board exams) is around $140k per year, which is basically what your family doctor is making. So he could be helping people and making 140k around age 25 (assuming he's 22 right now) or around 32 (and probably have gray hair and be totally burned out by then).
Anyway, this post is ridiculously long, sorry for that. Good luck to him in whatever path he chooses.