Temporary Guardianship

Definitely find a lawyer and get a legal guardianship drawn up. Then the child can legally be on your insurance, your taxes, and your social security. It it is temporary guardianship, you are almost nothing but a babysitter -- the bioparent can come back and reverse the guardianship at any time -- on a whim, or in anger if you refuse to loan them money for example. It is wonderful that you would consider taking the child, but don't set yourselves up for emotional blackmail.