He intended to do Hajj for himself, then he decided to change his intention and do it on behalf of a relative of his. Is it permissible for him to do that?

No File Exists
Check below answers in case you are looking for other related questions:
He did ‘umrah several times but did not do sa‘i, then he got married
Should he do more tawaaf or more prayers in al-Masjid al-Haraam?

No File Exists
Related Answers:
The status of Hajj in Islam, and the conditions of it being obligatory
The virtue of tawaaf around the sacred House
Is it permissible for the pilgrim in ihram to put a bandage on his knee because it is hurting him?
He did ‘umrah several times but did not do sa‘i, then he got married
Should he do more tawaaf or more prayers in al-Masjid al-Haraam?

Recommended answers for you:
Verses and hadeeth about hijab
Does anal intercourse cancel the marriage contract?
Why does Islam forbid lesbianism and homosexuality?
Rulings on menstruation
Ruling on trimming the beard because it looks scary