Enough of the down side, let's get some upside here. Needless to say there is nothing that is perfect in this world as a whole. This includes those that are trainers/coaches doing their own workouts. That being said working out with another person, and in my case, another trainer, will help you improve your workouts and get better results.
When working out with another person the one thing that most people would agree that is advantageous about this, even if the person has got almost no clue as to what to do with the workout, is motivation and accountability. Having your bro, coach, cousin, bookie or mail man work out with you helps keep you in check. Obviously the more experienced the person is with exercise and the exercises you are performing the better, but you really don't need too much for this purpose. Being versed in proper spotting technique would help as well, but any spot will help and I'm not getting into spotting techniques, just use your brain, or try to at least.
You say you are a coach or trainer yourself and know exactly what you are doing and how to do it well? I bet if I watched one set of one exercise that you did I could find something to fix to make the exercise better and more effective. I got humbled on this subject this past Saturday working out with another trainer I work with along with one of his buddies who also happens to be a coach. I consider myself huge on technique, learning it and then applying it to my clients and myself, but trust me I still got at least 5 ways to correct my technique in my workout that day. Needless to say everyone can get better, go look at some of the big guys in the industry they will tell you the same thing. Working out with someone else brings better results than working out alone. That's not to say don't workout if you don't have one, but if you have the chance to workout with a friend DO IT!
Will both you and your bro be able to stick with the program for years and years? One can only hope, but even if you don't, the time you are able to stick with it I will bet you will see some better results than you have experienced in the past, or at least rival some of your best results. In what has become a results based society, this is an easy way to see some of your results. Just find someone and you'll probably both learn something, directly or indirectly about fitness.
That's all I got today folks, glad to be back. Go out there and get after it!