Olivia Wilde shares new pictures of her 'mini man' son Otis

Olivia Wilde's baby boy is growing up fast! The House actress shared a rare photo with her 18-month-old son Otis on Tuesday, telling fans he was her "mini man".

The photo shows Olivia, who is engaged to actor Jason Sudeikis, cradling Otis in her arms as she tilts her head back and smiles. "Hugging it out with my mini man. Feels so good," she captioned the image.

Hugging it out with my mini man. Feels so good. 💆🏻

A photo posted by Olivia Wilde (@oliviawilde) on

Olivia Wilde shared an adorable photo of her son Otis

Olivia and Jason prefer to keep their son out of the spotlight, although the 31-year-old couldn't resist sharing a humorous photo of Otis wearing her bra on his head over the weekend. The amusing photo shows the youngster looking confused and raising his hand to his head where the underwear is resting.

"Hey, bra," Olivia wrote.

The actress is clearly smitten with her son judging by her social media posts and occasionally shares anecdotes about him with on Twitter, recently telling fans: "My son says goodbye to his toes every time I put his socks on."

Hey, bra.

A photo posted by Olivia Wilde (@oliviawilde) on

Otis is Olivia's first child with Jason Sudeikis

Olivia and Horrible Bosses actor Jason, 39, started dating in November 2011 and got engaged in January 2013 – they welcomed Otis Alexander in April 2014.

Jason opened up about their young son during an appearance at the Sundance Film Festival in January. "He smiles a lot," he told E! News. "I would say any looks he's got going – I feel like he's a real cute little guy – that's Olivia's doing. And then him smiling is both of us because we're really lucky."

The We Are The Millers actor added: "He's surrounded by love 24/7 and 80 per cent of it is female based. So I think he'll turn out to be a really good guy. I'm excited to see who he is."

Sick wardrobe on @latenightseth tonight. 👌

A photo posted by Olivia Wilde (@oliviawilde) on

Olivia occasionally shares anecdotes about her son on social media

Earlier this year, Olivia penned an honest article for Shape magazine addressing the unrealistic expectations women face after childbirth. "The truth is, I'm a mother, and I look like one," said the star – who admitted she's the "softest" she's even been.

"I believe in a world where mothers are not expected to shed any physical evidence of their child-bearing experience," Olivia added. "I don't want to waste my time striving for some subjective definition of perfection."