First off, the guy is kind of tense in all but the third shot. Especially the last one. It's like he's trying to smile but couldn't and just let out an awkward one. I think the most important thing in portrait photography is getting your clients comfortable, otherwise it's hard not get snap-shot-ish poses even if your composition is good.
Second, there's no character at all (maybe some teeny bit, but not enough for a portrait). Staring at the ring, staring at each other, staring at the photographer while sitting together. It just doesn't work if there's nothing you are emphasizing effectively.
For number 1, give the ring a sparkle or something, exaggerate its importance, give it more focus. Have her held it against the tree bark to make it stand out, and change the pose accordingly.
For number 3, the lighting is flat. And I already had enough of the guy's smile. If he can't smile properly make it serious. Just have them look into each other moderately, thoughtfully. Of course that might not work, but the point is, try to see what they are more comfortable in terms of expression. Don't go with anything that look too forced and unnatural.
I think I might've sound too discouraging, but false flattery is just going to waste your time and stall your talent.