Merhaba, I know that this is sad topic but it is also a part of life.

What do we say in Turkish if someone told us about death of his/her relative?
I have to send a letter to my far family in Turkey, please help me.

im sure their are more personal ones people can tell you, but these are just 2 i know of:

başınız sağ olsun-please accept my condolences

sizin için çok üzgünüm- im very sorry for you

chica's first phrase is a good one but the second isn't. Sorry chica. If it hadn't been an important issue I normally would not talk that clear and would say it smoother.

There are mainly two things to say:

1. Başınız sağ olsun.
2. Allah rahmet eylesin. << May God's mercy be with him/her.