Q: My parents are very old and have not made Hajj yet. Traveling has become difficult for them. Must they still go?
A: Whoever has met the conditions and is incapable of going without extreme difficulty due to old age or chronic illness etc., is required to sponsor whoever can perform ḥajj and ʿumrah for them from their nearby region in which they met the conditions of obligation. This appointment will suffice them even if they are cured after their proxy has entered iḥrām regardless if they completed the rites or not. Both are voided if they are unable to find a proxy.
Source: Hidyat al-Raghib