Now that he's growing into his own skin, he's showing some more personality. He doesn't attack the cat, which is good. But when he walks by, he definitely takes note and perks up his ears and stands up and wags his tail.
Unlike the other pups which, when he gets jealous he'll start barking and hog "us". He just does this airy whining when the cat is ignoring him and paces the floor uncomfortably when the cat is on the couch and he's on the floor. lol
He's slowly realizing the cat doesn't play. And that's okay. He's slowly learning to "leave it" and "enough" when he persists in whining or when he's jealous to share his space.