When I grew up my sister and I hung with a family that was less than ideal in many ways, all the men were alcoholics, the women long suffering, which all exploded into the occasional drama.  My mom, either through inertia (we were the youngest of 4) or wisdom, never made a big deal of it. Admittedly none of the family members were in jail...I think it gave us an insight into the lives of others, and an understanding how social conditions affect families.  I think our involvement with them gave the daughter the realization that she could achieve more and an impetus to  get a professional designation (it also helped that she was smarter than us.) She is still our friend 40 years later.

Studies show that a child from a dysfunctional background is often positively impacted by involvement with a caring adult  outside the family.

It is way too early to get excited by this friendship. Wait and see, it might be your kid's best friendship ever. And your involvement may really help this child.