سَلَّمْتُ عَلَى هَذَيْنِ الطَّالِبَيْنِ.
Translation: I greeted these two students.
عَلَى: preposition. هَذَيْنِ: genitive dual demonstrative marked by yāʾ. الطَّالِبَيْنِ: genitive apposition with yāʾ.
The form hādhayni occurs in both accusative and genitive; the governing context decides which.