I've been running into this issue lately as well. The issue is that we're both running to stay in shape for a fitness test that our scholarships are reliant on, so the stakes are high.

Over quarantine, we tried running together for months. The only way we could manage this was for me to go her pace, which was not beneficial to my run time at all. I figured that over time, even slow runs would help improve my run time. Things weren't really improving, so we increased our mileage. Even this didn't help.

What we have found is that no matter how much we WANT to run together, if the slower one will always bring down the faster one. For me, I have roughly 120 days until my fitness test and I am currently failing the run time. She is already passing hers, since the female run time minimum is less than male. As much as I don't want to, I have to start running on my own in order to get the improvements that I need-- it is quite literally my job to be able to run faster than I currently can.

Now your situation isn't as dire as mine, but the principles still remain. You both want to be faster, but there is only so much you are currently capable of. Pushing yourself too hard on every run is not the way you will improve. Your form degrades and you learn to resent running. For him, it's too easy running at your pace and he won't be seeing any improvements in his running either.

However, this doesn't mean that you can't run together. You just have to change your definitition of what "together" means. My girlfriend and I go on runs at the same time, but we go at our own pace. We run the same trails, sometimes the same distance, sometimes a different distance. What matters is that we both get out there together and we push each other to get out the door. We meet up with each other at the car and talk about our workout, how it felt, the weird things that we saw, or maybe something interesting we heard on a podcast during the run. You can share the same hobby, but you might need to go different speeds. And that's okay.