Is it proper to pray for a non-believer?

If you have a close family relation who claims to no longer believe in God and actually makes fun of God and those who believe, then is it a sin to pray for his welfare?  

A Muslim cannot pray for a nonbeliever to have a long lifetime, for their welfare or for their forgiveness. Because Allah (swt) stated that He will never forgive them:

“It is not for the Prophet, and those who believe, to pray for the forgiveness of idolaters even though they may be near of kin (to them) after it hath become clear that they are people of hell-fire.

The prayer of Abraham for the forgiveness of his father was only because of a promise he had promised him, but when it had become clear unto him that he (his father) was an enemy to Allah he (Abraham) disowned him.” (Surah al Tawba, 113- 114)

Asking for their forgiveness despite this fact is to object the ruling of Allah (swt) and blame Him with wrong judgement that is accepted as “blasphemy” by some of the scholars. (Qarafi, al Furuq) A muslim can pray just for their guidance. (Bazzaziyya, Hindiyya)