"Extreme hardship" is very hard to establish. The individual has to be very, very ill/disable and and you have to prove beyond the scope of clear emotional ties that the person really needs you. They want to see that you support this individual and his/her illness both emotionally and financially. They have a limit on the ppl who get this type of waiver but the amount of ppl who apply is ridiculous high compare to the ones who receive it. I vaguely remember that was what an immigration lawyer told me but I'm unsure if something has changed since 2012.

It is very hard to know anything other than what you hear from legal sources. So many ppl claim to have solve their immigration problems through this or that path (marriage, disable child, ect.) and then they get deported for being undocumented.