call them after their fathers. that is more just with allah. if you do not know their fathers then they are your brethren in the faith and your kinsmen. excepting what your hearts may intend deliberately there will be no sin upon you for any mistake that you may make therein. and allah is allforgiving allmerciful.
ادعوهم لآبائهم هو أقسط عند الله فإن لم تعلموا آباءهم فإخوانكم في الدين ومواليكم وليس عليكم جناح فيما أخطأتم به ولكن ما تعمدت قلوبكم وكان الله غفورا رحيما