can a person pray 4 the forgiveness of a faaaar away expired, christian relative?
No
It is not (proper) for the Prophet and those who believe to ask Allah’s Forgiveness for the Mushrikun even though they be of kin, after it has become clear to them that they are the dwellers of the Fire.(9:113)
this is the only ayah i found..does anyone else know of any
what about people who have christan families - i know many families where the mother is a christan.
Christians are Mushrik (polytheist) too in a way, because they believe in the trinity.
The Christians who are the saved ones, the ones “on whom there shall be no fear nor shall they grieve” are the true followers of Jesus :as:, prior to the advent of Muhammad :saw:, the ones who believed in monotheism, an example was Waraqah who was a cousin of Mother Khadija 
, the Prophets :saw: first wife.
When Muhammad :saw: started his mission, all prior past religions which were revealed were abrogated and anyone who stuck to them was doomed, same way the true monotheistic followers of Moses :as: are saved but when Jesus :as: came with the message of God, Jews were suppose to accept him as the Messiah, a Prophet, Messenger of God and a Word from the Lord born to the Virgin Mary (pbuh), those who never accepted this were doomed.
The only acceptable religion in the sight of God today is Islam and He will forgive anything except partners being set up with Him, monotheism is the reason for our creation, part of monotheism is accepting His sovereignty over us and the rest of creation by accepting His religion.
Those Christians and Jews in your family who are alive you may pray for them so that the Lord shows them the Light of Monotheism but once they died I’m a afraid there’s nothing we can do.
It is no harm in praying for any body.
That is GOD who know the DILOUN KA HAL AHWAL.
May be that christian is better than many so called showing off muslims, in the eyes of GOD.
May be at the time of his death he has thought right. Who knows?
Every thing GOD and but GOD knows. We are just smaller than a fundamental particle of an atom. HAMARE HASYAT KEYA HEI KHUDA KA SAMNEY< HUM KOUN HEIN KA YE SOUNCHEIN KA WOU BURA HEI AND BUS HUM ACHHE HEIN.
Doua karney walay kay bhei hasanat likhey jatey hein. Agar douwa qouboul na hou tu us khaliq key merzi. HUm tou bus razi ba razaei khuda houn gay.
^
Read the Qur'aan and then open your trap. :)