Neil Patrick Harris has shot down rumours he's splitting from his fiancé.

The 41-year-old actor has silenced speculation his relationship with David Burtka is on the rocks by posting an adoring picture on Instagram of his beau and their four-year-old twins Harper and Gideon.

He accompanied the snap with the caption: ''I couldn't be more in love with my family. Any reports to the contrary are woefully mistaken. #grateful (sic).''

However, the 'How I Met Your Mother' star admitted recently that his relationship with David, whom he has been dating for 10 years, has changed over time.

He told Glamour magazine's September issue: ''Honeymoon phases end. They just do. We're animals, and animals aren't inclined to copulate with just each other for the rest of their lives.

''So here's a challenge: How do you keep redefining your relationship? I think you have to find new elements that turn you on, and not only sexually. Having kids was one of those great moments for me.

''Watching David become another level of person, mastering this other domain, made me look at him with a whole other set of appreciative eyes. That sort of made me re-fall in love with him.

''That's another important thing to realise. Everyone falls out of love with everything. You fall out of love with your house. You fall out of love with your job. You just have to figure out ways to keep [the love] alive.''