Sienna Miller's father is battling Alzheimer's Disease.
The Hollywood star's elder sister Savannah Miller shared the heartbreaking news on Sunday as she paid tribute to their father amid his ailing health.
Alongside a picture of their father, former art dealer Edwin Miller, Savannah shared a heartfelt Instagram post, stating that she 'missed him beyond description.'
She penned: 'here he is.. my papa, the man with the deepest heart, wisest words and the most incredible hug giver to ever live. I miss him beyond description.
'As his Alzheimer's progresses and he slowly withdraws from the world, my heart aches for this man. His hugs are still as deep, thank God, but the life and spark, that was all pervading, has gone out.'
She concluded: 'It is such a cruel and complicated thing to navigate. Sending love to everyone for whom today is hard. #fathersday #alzheimers.'
The Miller children have been rallying around their father as he battles dementia.
In March, Sienna, 41, joined bridal wear designer Savannah, 44, in New York, where they huddled round their father with his sons, Stephen and Charles, from a previous relationship.
'For the first time in six years, we're all together with our dad,' Savannah penned. 'A lot has changed in that time, with his declining health, but at the same time nothing at all.
'Love feels the same, as deep and true as it ever did. We may be oceans apart but our love for each other and our papa transcends it all.
'In these very real moments, I am reminded, gracefully, what it is all about. Love and human connection is all we ever truly have and I am deeply grateful for the love and connection I have with these four remarkable human beings, my family. ??'
The sisters' mother is ex-model Jo Miller, who was married to Edwin until 1987. He went on to marry the interior designer Kelly Hoppen.
When Sienna moved back to New York City, she found comfort in living closer to her father Edwin once again who remained living and working in the Big Apple.
In 2015 Edwin was a pillar of support to Sienna when she went through her break up from Tom Sturridge, who is the father of her 10-year-old daughter Marlowe.
She has since mended her heartache and is loved-up with boyfriend Oli Green, 25, who she has been linked to since 2022.
After three broken engagements, Sienna was rumored to be dating Oli after they were seen attending the BAFTAs together and enjoying a New York Knicks basketball game.
The pair were also photographed posing on the red carpet together at the Vanity Fair Oscars Party.