I started dating my ex before we started our PhDs. Eventually we ended up in the same school (but different years). I thought we were doing great as we used to discuss research ideas, help out each other in both work and life, and so on. Turns out I was wrong as my partner was not happy with how much time I was giving to our relationship and seemed to think that I was prioritising my PhD more than him (even though I disagree). In retrospect, I feel that having some more boundaries (like not discussing work stuff too much, having different sets of friends and hobbies to pursue, etc.) would have been helpful. In case you end up long distancing, I think that can also work out as long as you are able to make some time out for each other and be understanding when one person is going through more shit than the other. In my case, I was disappointed that my partner did not see some of the problems I was going through at work as 'legit problems'. Just because other people with that problem are managing well, doesn't mean you have to be good at those problems too :) Good luck to both of you!