Of course it's hard to tell wether it's Latias or Bianca who kisses Ash.
More like Crowning Moment Of Cute. After Ash and Latias start playing with each other, Latios flies over to Pikachu. Pikachu shrinks away from it, then as Latios starts moving his head towards Pikachu, Pikachu shuts its eyes. It turns out that Latios just licks its face to make up for attacking it earlier.