Congrats on the baby, that is a huge blessing
. I do not know your school's COA or if you have taken a loan in the past as some loans have an aggregate lifetime borrowing limit which determines how much you can use for federal direct unsubsidized loans. You will likely max that out regardless because they have a limit of I believe 47k/yr (that is what I got, at least), so you will have to take out a graduate plus loan.
The grad plus loan does a credit check so make sure you have good credit or have a co-signer ready. The graduate plus allows you to borrow the COA minus any other loans (i.e. federal direct unsubsidized). If whatever is left is not sufficient for you to live and take care of your baby and wife, you will have to petition to your school for more money (not always granted) or take out a private loan. Although you are looking for a precise amount X of how much excess people have after paying for school, the answer is not straightforward due to differing COA's, cost of living's in different cities, having kids, etc. Best of luck to you in school and as a parent as well!
TL;DR: you will more than likely have to petition to your school for more money or take out private loans. When they factor in COL, they consider expenses for one person ( student), but you will be paying for 3 ppl.