I was just thinking today that Jack the Giant-Killer and Rapunzel would work well together logistically speaking (plant bean, wait, no need for hair or silken rope ladders), but I hadn't got as far as thinking about their interpersonal relationship because actually the story I'm working on is a Rapunzel/Sleeping Beauty/(Romeo and)Juliet/Lady of Shalott crossover (with possible Highwayman's Bess to be confirmed).

But really it seems to me that Jack just isn't ready to be thinking about romance just yet. Rapunzel probably shouldn't either given that she's like 15 but these things happen when you're lonely I guess.