Is there any connection between Kankri and Meulin that would've become the relationship between the Signless and the Disciple?

Nope, Kankri was surprised about it too even saying in a conversation with Latula: “with… Meulin, 9f all pe9ple? 6ut that’s neither here n9r there. #Seri9usly. #I mean, she’s nice, 6ut… #Really?“