What is the ruling on a housemaid seeing the 'awrah of a 12-year-old physically and mentally disabled boy, and is it permissible for any of his family members to do so?

It is not permissible to expose one's 'awrah except in cases of necessity or need that are considered equivalent to necessity. Washing a paralyzed person and changing their clothes falls under this category. This should be done by their parents first, then their siblings, then a male attendant, and if that is not possible, then a female attendant. The guiding principle is the Almighty's saying: "So fear Allah as much as you are able." The person performing the washing should lower their gaze as much as possible.