Extreme hardship is legal standard for 601 and 212 waiver and refers to, as the term indicates, abnormal situations. “Extreme hardship” is very vaguely defined as greater than the normal hardship the qualifying relative can be expected to experience if the alien is denied admission. It is important to prove both why the qualifying relative cannot move abroad AND why the qualifying relative cannot simply live in the US without the alien. For instance, It is not enough to say that the qualifying relative will miss the alien’s company as this is considered “normal” hardship, not extreme hardship.
BIA eventually identified five general groups of factors to be taking into account by any reasonable adjudicator making extreme hardship determination. Based on precedent cases, major medical condition of US relative, such as brain tumor, multiple sclerosis, cerebral palsy, or elderly, chronically ill, or disabled US relative makes strong arguments. Others don’t.
It can’t be stressed enough that it is insufficient to prove that Relative has elderly or sick relatives. You must show the link between the medical condition and the waiver, i.e. you must prove that the elderly or sick person needs the qualifying Relative to remain in the US and, preferably, that the Alien is also needed in the US.