While Jack definitely idolizes his uncle and is starting to adopt Jervis’ moral code, up to and including murder, one thing they disagree on is romance.
Jack grew up in a loving household. His parents were never scared of showing affection, they've always been the couple who held hands on park benches while watching their son play, talking and laughing with each other. They're the type to tell Jack the tale of how they met as a bedtime story.
Jack knows what love, real, true love, looks like. He’s seen for himself that happiness is people who would give each other the world, but who would never ask for it. Of course, he’s still young, so he still doesn’t get it one hundred percent, but he’s very sweet and understanding to anyone he falls for, even moreso than he normally is to people he’s not actively targeting for a crime.
Really, while Jervis is ‘If they can’t be with me, then they can’t be at all!’ Jack leans VERY hard into ‘I want my beloved to be happy’ territory
he’s a SIMP! a big ol sweethearted SIMP!!! YEAH sure he’ll kill anyone who bothers the object of his affections, but he’ll back off without hesitation if they ask.