In some ways it is tougher, with childcare being the biggest factor. If you are in the US, a number of states have childcare subsidy programs for parents who are working or are full time students, though you need family income below a certain level in order to qualify. In my case we were able to qualify for a small subsidy my first two years, and it was enough to keep us from having to go into debt (in my third year my wife received a promotion with a significant raise at her job). Some universities have discounted childcare available for graduate students. Email or call them to find out.
No matter what, you will have less time available to study than single students without children. On the other hand, having family to emotionally support you is a big help - PhD students have some of highest levels of anxiety and depression and having a supportive significant other and having children to play with and distract you at times definitely helps.
Whether to buy or rent depends on where you live. But many universities have some form of graduate student family housing for full time students who are married and/or have children, and this is usually cheaper than renting in the area especially after utilities are taken into account.