Its not just the fact Cardan hints to Jude about Locke & Taryn. It’s the fact that in almost every single conversation Cardan has with Jude, he hints at it. Even in their first interaction after he’s found out. I swear to god.
[ID: An animated gif of Jonathan Sims of the Magnus Archives. He has brown scarred skin, and short grey hair and a moustache. He's wearing a brown hoodie with cream colored sleeves and pull strings. Jon happily pulls the hood over his head and flips the little cat ears on top of it upright, one at a time, saying meow each time. The background is pink with pink paw prints dotting it. The short animation loops over. \End ID]