When singer Jesy Nelson, of girlband Little Mix, and her much younger on-off rapper boyfriend Zion Foster announced in January last year that they were expecting identical twins, the news was met with joy by their collective 10 million Instagram followers.

Yet that joy soon turned to tragedy. Earlier this month, Jesy revealed that both baby girls, Ocean Jade and Story Monroe, were born prematurely with a rare genetic disease called Spinal Muscular Atrophy Type 1 (SMA1), which causes progressive muscle weakness and wasting. The terrible condition could leave the twins unable to walk, talk, eat or drink, and requiring round-the-clock care. Were it left untreated, their life expectancy could be as little as two years.

It was Jesy’s mum, Janice White, who first spotted the early lack of development in the girls, despite visits from health workers who insisted the girls were doing ‘great’.

It’s any mother’s nightmare. And as if that wasn’t devastating enough, then came the news that Jesy, 34, and Zion, 26, have separated, four months after announcing their engagement.

Friends claim that despite no longer being together, Jesy and Zion are committed and remain ‘fully united to co-parent’ their twins. They are solely focused on ‘what’s right for their daughters’.

The rapper who, like any dad in his position, maintains hope that his daughters will defy the diagnosis, even penned a poem to Ocean and Story – which he posted on his Instagram page – describing them as his ‘two little warrior girls who already know how to fight’.

Jesy and Zion in hospital after the birth of their twins, Ocean Jade and Story Monroe

Zion penned a poem to Ocean and Story – which he posted on his Instagram page – describing them as his ‘two little warrior girls who already know how to fight’

It is not known who ended the relationship; all that is certain is that Jesy faces a frightening future caring for her daughters as a single mum, despite claims from Zion that he will ‘always be there for her and them’.

So, how exactly will that work? Both Ocean Jade and Story Monroe, now eight months old, require full-time, specialist care.

Jesy, worth an estimated £6million, has revealed her £3million Essex mansion now contains so much medical equipment it resembles a hospital wing, including breathing machines and feeding tubes. The girls also receive physiotherapy to stimulate their wasting muscles.

Despite the turmoil she is undoubtedly going through, Jesy has spoken openly about her daughters’ diagnoses and is campaigning to have an early test for the condition made available on the NHS. If it is caught early then the progression can be slowed or even prevented. She is also remaining positive and focusing on her girls’ happiness.

Which brings me to the question: how will Zion fit into her life as a ‘hands-on’ dad, as he says he will be, if they are no longer together?

It’s hard to be ‘hands-on’ if you don’t live with your daughters. So, despite his honourable intentions, can the young rapper really fulfil that promise?

Zion has been billed as one of the UK’s most exciting up-and-coming R&B artists, collaborating with global stars such as Patoranking and Zlatan (no, I’ve never heard of them either). How will he manage to balance this burgeoning career – that started with making rap music in his bedroom – with being a full-time father to two severely disabled daughters?

Only time will tell whether he will be just another part-time dad breezing in when it suits his recording schedule… though I hope he does come through for his daughters and for Jesy.

But we all know tales of fathers who make the same promises when they split from the mother of their children – to always be there, to co-parent – and then, when it comes down to it, just turn up for high days and holidays, leaving all the hard graft to Mum.

Jesy and Zion introduce their twin girls on This Morning last summer, before their diagnosis

Jesy and Zion’s twins were born prematurely with a rare genetic disease called Spinal Muscular Atrophy Type 1 (SMA1), which causes progressive muscle weakness and wasting

One campaigner for families with disabled children, Sam Carlisle, who has a daughter with a rare genetic disorder, warned after hearing of Jesy and Zion’s ‘co-parenting’ plan that ‘relationship breakdowns are more common for parents with disabled children’.

‘The family life you imagined evaporates, replaced by one no one prepares you for,’ she added. ‘Those gorgeous girls are going to need their mum and their dad in lockstep, fighting the many battles they will face in the future.’

Zion, take note.

I hope that the rapper’s poignant poem to his daughters reflects his determination to be a good father to them: ‘Story, is your heart OK? Ocean, how’s your mind? Honestly, my worry isn’t the milestones… my worry is quieter than that, deeper. It’s about accepting you, loving you for who you are right now, without conditions.’

Yes, it’s hardly Shakespeare. But here’s to hoping and praying Zion is man enough for the task – and that Jesy isn’t the one left holding her babies, alone.