رَأَيْتُ أَخَاكَ خَالِدًا.
“I saw your brother, Khālid.”
رَأَيْتُ: past verb with first-person subject suffix.
أَخَاكَ: accusative direct object with alif; muḍāf, with possessive kāf.
خَالِدًا: accusative explanatory apposition with fatḥah.
The apposition is accusative because the antecedent is accusative, not because all explanatory followers must be so.