Will the brother, sister, and girl be sinful when they aborted the dead fetus resulting from an illegitimate pregnancy and did not bury it after the abortion, and what is incumbent upon them?

If trustworthy doctors testify that the fetus was dead before the abortion and the abortion was not the cause of its death, then there is no harm in aborting it. However, if it died due to the abortion or an act by the woman before the abortion, then the woman owes the blood money (diyah) for the fetus, and the diyah is due from whoever performed the abortion. It is not permissible to discard the fetus without burial. The woman and whoever assisted her in the abortion must engage in sincere repentance.