My girlfriends sister and husband want to sign over their parent rights to her.

So we live in illinois.

Her sister is 21 with POTS and a slew of mental health issues and doesn't work. her husband is the sole income and works 50 hour weeks. They both are young and aren't able to take care of the child the way he needs.

Both of us agree that we would take him in, but not sure how to go about it. We've never done this. I was thinking guardianship in case they change their mind, but my girlfriend has said they both agreed to sign over their rights.

What are the steps we need to take?