Changing children’s last name
10-7-2016 | IslamWeb
Question:
Assalaam alaykum. My question is concerning taking a last name different from that of your father. A brother's parents divorced twenty years ago because of a lot of problems. The father stabbed the mother with a knife and other bad things. The mother changed the last name of the children for security reasons and ignored the Islamic ruling. The children have a different last name, but the Dutch government knows the father of the children. How can the mother and children repent? What is the solution? They cannot changed it back. Allaah willing, you can answer the question directly.
Answer:
All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.
It is impermissible to attribute the children to other than their real father by doing what this woman did. The fatwa of the Permanent Committee for Islamic Research and Fataawa reads:
“The Prophet, sallallaahu ʻalayhi wa sallam, prohibited attributing anyone to other than his real father or to falsely claim to belong to a family or tribe. Abu Tharr 
reported that the Prophet, sallallaahu ʻalayhi wa sallam, said, 'If somebody knowingly claims to be the son of any other than his real father, then he but disbelieves in Allaah, and if somebody claims to belong to some folk to whom he does not belong, then let such a person take his place in the Hellfire.' [Al-Bukhari and Muslim]”
Al-ʻAyni 
wrote, “The hadeeth 'and if somebody claims to belong to some folk to whom he does not belong' underlines that it is prohibited to falsely claim to be a descendant of a family or tribe while one actually has no blood relations with them...” [ʻUmdat Al-Qaari]
However, since she did what she did while ignorant of the religious ruling in this regard, then we hope that she bears no sin for it. Mistakes are pardoned by the will of Allaah; Allaah, The Exalted, says (what means): {...And there is no blame upon you for that in which you have erred but (only for) what your hearts intended. And ever is Allaah Forgiving and Merciful.} [Quran 33:5] Nevertheless, she must try to set the record straight and strive to attribute the children to their real father. If she cannot do that officially, then she should preserve this fact through witnesses or so in order to avoid any potential loss of rights as well as the mixing of lineages.
Lastly, we would like to point out the gravity of marital problems and disputes between spouses. They should adhere to wisdom and reason and keenly seek to solve their problems through dialogue and mutual understanding for the sake of their family; otherwise, they will regret not having done so once it is too late.
Allaah knows best.