• كِلَاهُمَا
• كِلْتَا

Appears 2 times in the Quran.

1. 17:23 وَقَضَىٰ رَبُّكَ أَلَّا تَعْبُدُوٓا۟ إِلَّآ إِيَّاهُ وَبِٱلْوَٰلِدَيْنِ إِحْسَٰنًا إِمَّا يَبْلُغَنَّ عِندَكَ ٱلْكِبَرَ أَحَدُهُمَآ أَوْ كِلَاهُمَا فَلَا تَقُل لَّهُمَآ أُفٍّ وَلَا تَنْهَرْهُمَا وَقُل لَّهُمَا قَوْلًا كَرِيمًا

   And your Lord has commanded that you shall not serve (any) but Him, and goodness to your parents. If either or both of them reach old age with you, say not to them (so much as) "Ugh" nor chide them, and speak to them a generous word.
   

2. 18:33 كِلْتَا ٱلْجَنَّتَيْنِ ءَاتَتْ أُكُلَهَا وَلَمْ تَظْلِم مِّنْهُ شَيْـًٔا وَفَجَّرْنَا خِلَٰلَهُمَا نَهَرًا

   Both these gardens yielded their fruits, and failed not aught thereof, and We caused a river to gush forth in their midst,