Hi,
My wife and I started scuba together and have been tight buddies since.
Our initial OW pool training was separate to start with until it was clear what our competence and comfort levels were, and it gave the instructors a chance to see how we interacted in a training setting.
Near the end of OW, and ever since (OW open water dives, AOW, wreck, drysuit, nitrox to date) we have trained together, which is good since we dive together.
You will have to know, understand, and accomodate each other's learning styles and progress rates. My wife and I have both been teachers at various times in our careers, so we understand pedagogical theory and how to detect and respond to learning styles (though even with that said, it takes some self-control self-awareness to step back in the middle of it and do that for oneself!).
My own fundamental belief is that you should be able to train with your primary buddy, else you have a bigger problem! That said, it may not be easy to find the right rhythm, but it is important to find out how to make it work.
Cheers,
Walter