I don't know of many good stories of folks who married while still in school. I'm sure some folks succeed, though. I honestly think you need to wait awhile--at least finishing undergrad school first. In grad school he will be very busy and occupied.
Life will always be stressful with something. School can be more stressful than work, I think. My sons say they want to get out of grad school before settling down. I was later in my marriage, so maybe they are following my example. I was finished with grad school and had worked for 8 years before marrying! I was 33. We just don't know what the future will hold.
My thoughts on it, anyway.