Duck Dynasty dad Willie Robertson snuck up behind daughter Sadie and her boyfriend Blake Coward in a hilarious photo posted on Instagram.

Sadie, who finished second in the last season of Dancing with the Stars, regularly posts fun pictures of herself with her beau and it looks like after nearly a year together, the young couple are as strong as ever.

In a cute picture shared to Instagram, a smiling Sadie is holding an umbrella over the pair and has one arm casually slung around Blake.

Willie can be seen peaking out from behind the stylishly-attired pair holding a drink and sporting a giant grin.

Sadie took her father's gatecrashing in good humour, captioning the photo: "What's a picture without a photobomb."

Sadie met Coward, a senior quarterback, while attending a softball game at Madison Academy in Alabama.

Sadie recently revealed in an interview that her dad warned Blake against hurting her. He reportedly said to Blake, "You hurt her, I'll hurt you. I'm watching you like a hawk, and I'll break your legs if you do anything to her."

Coward recently revealed that he had to adjust to all the new attention after he started dating his famous girlfriend. His Instagram followers shot up to over 110,000 and he is apparently regularly swarmed by girls who want to take selfies with him.

Reflecting on the attention he gets dating a celebrity, he said: "It's definitely weird. It kind of happened all of a sudden; it didn't happen gradually. As soon as we started dating, it just kind of hit me,"AL.com reports.

And although Sadie may regularly share photos of her and Blake embracing, the young star insists sex is something that should be saved for marriage.

"People are like, 'It must be easy for you because you're Christian.' That doesn't make it any easier for me. And it's something a couple really has to decide together," she recently told Us Weekly.

"I don't really date guys who don't feel the same way. It's going to be way harder if we went into a relationship having different opinions about that. So going into it, Blake felt the same way. He's raised in the same kind of family as I am, the same kind of church."