Ik denk aan mijn familie. (I think of my family.)
denken takes "aan" (denken aan = to think of). Example: Ik denk aan mijn familie. (I think of my family.)
Ik denk aan mijn familie. — I think of my family. The preposition aan is fixed, so it doesn't change with the sentence.
Fixed prepositions come up all over the A2 exam. The platform drills them in real exam tasks, AI-graded across all five DUO sections.