Saadat Lineage
They were the real daughters of the prophet. In the Quran, in Surah Ahzab, God has stated that do not call your adopted children as your own. They should be called after their real fathers. ادْعُوهُمْ لِآبَائِهِمْ هُوَ أَقْسَطُ عِندَ اللَّهِ and then God has mentioned that daughters of the prophet which is a clear proof that they were the daughters of the prophet. يَا أَيُّهَا النَّبِيُّ قُل لِّأَزْوَاجِكَ وَبَنَاتِكَ وَنِسَاءِ الْمُؤْمِنِينَ يُدْنِينَ عَلَيْهِنَّ مِن جَلَابِيبِهِنَّ ۚ ذَٰلِكَ أَدْنَىٰ أَن يُعْرَفْنَ فَلَا يُؤْذَيْنَ ۗ وَكَانَ اللَّهُ غَفُورًا رَّحِيمًا Moreover, Arabs were very particular of keeping the record of their lineage. This very cautiously recoreded it in the books of Ansaab available to consule. They mentioned the daughters of the prophet as his own. It is not possible that they might confused the lineage of the daughters of the prophet who was the most prominenet figure. It is unfortunately due to some politcal and secterian motives of a certian factions who, to make make the descendants of Hazrat Fatima as the only rightful heirs of the prophet, innovate the idea that other daughters of the prophet were not his.