Willow Dunn was allegedly left to starve to death in her cot while her father and stepmother doted on their new baby.
The tragic four-year-old's dad, Mark James Dunn, 43, and his girlfriend Shannon White, 43, were both charged with murder after the girl, who had Down syndrome, was found dead in a back room of their Brisbane home on Monday.
Their own son was born on August 30, 2018, and from all accounts was loved and adored by both his parents.
White posted numerous photos of herself and the little boy to Facebook including a recent video of him happily playing with toys on the floor.
'Running a muck (sic) has just learnt how to get in the sunroom lol,' she wrote, while Willow at the same time was allegedly being horrifically neglected.
Shannon White, 43, holds her toddler son, born August 2018, whom she shares with her boyfriend Mark Dunn
Willow Dunn, 4, was the daughter of Dunn and his deceased wife Naomi. In contrast to her baby half-brother, her body was found decomposing in her bed and police revealed she died of malnourishment and sustained neglect
Photos from the birth of the baby the accused killer's share prompted friends to comment how much he looked like his father - Dunn. 'Definitely has Mark's ears, lips and nose,' White replied.
Dunn and White posted numerous selfies of each other, tagged each other in couples' memmes, and left gushing emotional comments with heart emojis.
White was the best friend of Willow's biological mother Naomi Dunn, who died on November 5, 2015, from complications in giving birth to her.
Little more than a year later in early 2017, White, who was Ms Dunn's best friend and a bridesmaid at her wedding in 2014, moved from her home in Adelaide to Brisbane to shack up with Dunn.
Little more than a year after Ms Dunn's death in early 2017, White - who was Ms Dunn's best friend for 20 years, moved from her home in Adelaide to Brisbane to shack up with Dunn
White (centre) was on Wednesday arrested and later charged with murder. Dunn had been slapped with the same charge a week earlier
White was led away from the station in handcuffs looking worse for wear and wearing thongs and shabby clothes
Their union appeared to have the blessing of White's family and friends, who often remarked how 'handsome' Dunn was.
'Perfect couple! Look so happy together and they both certainly deserve each other,' one of White's adult daughters wrote.
Willow's seven-year-old elder brother was also well cared for and there appear to be no signs of mistreatment towards him.
Meanwhile, Willow, who suffered from Down syndrome, was allegedly left to lie in her own filth for days or weeks on end while they played with the new baby.
They allegedly left the helpless little girl lying in her bed, starving to death, long enough for her to have infected sores on her hips down to the bone.
White gushed over Willow when she was born in late October 2015, when she posted this photo of the newborn infant
'My best mate's baby willow such a beautiful sole (sic) can't wait to meet her, so adorable,' she wrote
White allegedly told police last week that caring for Willow, who had Down syndrome, was not her responsibility as she was not her biological daughter.
She also gushed over Willow when she was born in late October 2015, when she posted a photo of the newborn infant.
'My best mate's baby willow such a beautiful