I'm a married international student, although no children. Lots of thoughts right now regarding how long it might take for my wife to get a work permit, and when she does, if she's going to find a suitable job. Luckily she finishes her degree this spring, so we're hoping there won't be much trouble finding something. As closetchem mentioned, it's probably a good idea to discuss the family situation with potential PIs and to make sure that their demands are compatible with family life. From my experience, to free up time for their families married students and students with children often push themselves rather hard in the lab. I think it's important to find a PI who understands this, or at least sees the effort put in and the results produced, rather than just looking at the amount of clocked lab hours.