Kurt has been in a relationship with Kate's mother Goldie for 30 years and although the trio are extremely close, Kurt says they don't offer advice unless Kate asks for it.
He explained: "We stay out of their way, obviously. But if we find ourselves talking about each other and how we feel about each other, we stand up and we say, 'Wait this is important!'
"I'm not going to lie about something like that, and we try not to stick our nose in where it doesn't belong, but if we sense that perhaps there is something that someone wants to talk about, I think we're open enough to say a little something if it's right and appropriate."
Although he and Goldie have been together for so long, Kurt doesn't have any tips for how Kate and Matt - who have an 18-month-old son named Bingham together - can emulate them.
He added to People: "I don't know what secrets there are, and like any couple that's been together for 30 years, we've experienced many, many different angles and avenues of our relationship.
"I think I'm incredibly lucky to have had the experience, and even more fortunate to have it with the person I have it with."