Have them look into the camera when directly addressing the bride and groom for later viewing, like if it is a good-luck wish. If you’re interviewing them at length to get them to tell a longer anecdote, eyeline off to the side usually works better, is more formal and impersonal, detached. More like a documentary style. But no law says you can’t mix and match.
The other thing to do is change the width of the shot between answers, while you’re asking the questions, so that when you cut out the questions, the answers, edited together, flow naturally. What makes this work is asking questions that cannot be answered in a “yes or no” manner, but HAVE to be “essay answers”, that “put the question back into the answer”. If they still give you monosyllabic answers, ask follow-ups like “why”, “How is that?”, “What’s the reason for that?””What happened that made you decide that?” “How does a person get to do what you do?”. Leading questions.
Example question: “What’s your favorite ice cream?”
Wrong way answer: “Rocky Road”
Right way answer: “My favorite ice cream is Rocky Road, because, it has nuts, chocolate, marshmallow, all these different textures that work together…etc etc etc.”
See, you can EDIT something nice out of sentences like that. Try editing monosyllable answers together, without the question to explain what you’re asking them… it’s horrible.
I knew a news cameraman who stuck a little fuzzy mini-figure on top of his viewfinder: he found that it always made people look towards the lens but not quite into it, and they tended to look into his lens more than any guy on either side of him, because that incongruous little troll doll or whatever it was was an eye magnet. It worked especially well when interviewing children.