Praise be to Allah.
The Muslim is not obliged to pay for his wife or either of his parents to go for Hajj, because his duty with regard to his wife and parents is to spend on their food, drink, clothing and shelter. But if a Muslim wants to donate the cost of going to Hajj to anybody, he should start with his mother, then his father, then his wife, because of the hadeeth of Abu Hurayrah (may Allaah be pleased with him), according to which a man came to the Messenger of Allaah (peace and blessings of Allaah be upon him) and said, O Messenger of Allaah, who is most deserving of my good treatment? He said, Your mother. He asked, Then who? He said, Your mother. He asked, Then who? He said, Your mother. He asked, Then who? He said, Your father. Ibn Shubrumah and Yahyaa ibn Ayyoob said: Abu Zurah told us something similar.(Reported by al-Bukhaari, 5514). And Allaah knows best.