Aang is quiet as he processes all of this. Helping, or not depending on one's point of view, is the fact that each name elicits a memory in the back of his mind to jog.

Zuko and I...

A mental image of Wan and Zuko kissing appears.

Katara and Sokka...

The last time he saw the each of them. Sokka before the battle, Katara as he left to go home.

Katara and Zuko...

The look on her face after they walked in on Zuko and Wan.

"...oh."
Well...this is awkward.