Sienna Miller, 44, shares first photos of her newborn baby and toddler as she and exhausted fiancé Oli Green, 29, give rare insight into the realities of 'adulting'

has shared the first photos of the two children she shares with her fiancé Oli Green.

The actress, 44, made a low key announcement in May that she had welcomed her third child, simply saying: 'It's happened. I have a tiny baby next door.'

On Wednesday she posted photos of their whirlwind first few weeks as a family, under the caption 'Adulting.'

The snaps show a blissful Sienna cuddling her newborn in hospital after the birth. The couple are yet to reveal her third baby's sex or name.

She also shared her first photo of the two-year-old daughter she shares with Oli, posting a sweet snap of her toddler's curly hair. 

In another photo a heavily pregnant Sienna rests in bed with her bump on show. Childhood photos of Oli along with toys and sports memorabilia cover the shelves, suggesting the couple retreated to his childhood home shortly before the birth. 

Oli also appears in several photos, looking emotional as he held his baby in hospital before pushing the pram near the couple's London home. 

Oli shared his own look at the realities of life with a newborn on Wednesday, uploading selfies of himself with bags under his eyes alongside the caption 'parenting'. 

Sienna is now a mother of three, sharing daughter, Marlowe, 13, with ex-partner . 

She announced her third pregnancy by revealing her blossoming bump at the star-studded  in December. 

In May, she said that she's surviving on 'very little sleep' as she opened up on returning to work just three weeks after giving birth while appearing on The Tonight Show With .

During her appearance on the show she opened up about the transition of having another child and spoke about her nightmare flight over to the US to promote new action movie Jack Ryan: Ghost War.

Sienna said: 'It feels like stringing sentences together is a bit challenging. I'm on very little sleep but I'm madly in love with my baby.

'It's crazy to be talking words and wearing a dress. What has happened from pajama gate.' 

Asked by the host which of her children are tougher to look after, she said: 'I would have said the teenage girl would be harder to juggle until the transatlantic flight I took yesterday with the toddler and the newborn. 

'The toddler now wins hands down. It was an absolute disaster. There's no negotiating. I got to the immigration line and just broke down.'

Last month Sienna's sister Savannah confirmed the actress is engaged to Oli. 

In an interview with Hello!, fashion designer Savannah praised 29-year-old Oli's beautiful proposal. 

Savannah said: 'We are all so over the moon. It's the happiest news, and it was beautiful, the whole thing. I can't express how happy I am for her.'

Rumours of Sienna's engagement began the week before when she stepped out with a new diamond ring on her wedding finger.

She showed off her eye-catching jewel on a trip to Barcelona, where she was seen leaving a party only a week after giving birth.

It is the fourth time Sienna has become a fiancée, although she has never yet been married.

Friends of the couple say former model Oli has long made known his desire to marry Sienna, despite being 15 years her junior.

One said: 'Oli and Sienna are so ridiculously in love, they've got a lovely family and have such a giggle together.

'He knows what a catch Sienna is and wants to make her his wife. Hopefully it will be fourth time lucky and Sienna will make it to the aisle this time.'