What are the real thoughts on who Littlefinger says is "a young handsome boy"?

My first thought was Lancel, but Lancel is already apart of the Faith Militant and with the High Sparrow. Littlefinger doesn't have any clout over Lancel.

I now have two theories: Robyn Arryn, because that would be a fantastic alliance for the Reach and the Vale to come together, and then my other theory...

Aegon.

Could it be possible in the show universe that they rotated the roles so that Littlefinger has been supporting Aegon, Varys for Daenerys, and just dropped Illyrio all together.

Any show evidence that could support Aegon and Littlefinger? Or at this rate, Trystane?