A man who had already been separated from his wife for more than two years when he struck it rich has been ordered to hand over half.

Rich Zelasko, from Pontiac in the US, won a life-changing $US30 million ($A43 million) after buying a $1 Mega Millions lottery ticket in 2013.

At that stage, he and his ex-wife Mary-Beth Zelasko had been separated for well over two years, and the couple were in the middle of divorce proceedings.

Mrs Zelasko and her lawyers believed she was entitled to half the winnings, and an Oakland County Circuit Court judge agreed, ruling in her favour, news.com.au reports.

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According to the Associated Press, that decision was appealed — but now, the Michigan appeals court has also sided with Mrs Zelasko and ordered her ex-husband to hand over $US15 million ($A21.6 million).

That's because arbitrator John Mills ruled the lottery jackpot was considered "marital property" at the time of the win because although they were separated, the Zelaskos' divorce had not yet been finalised.

That meant their separation wasn't legally recognised, even though official proceedings were underway.

"It's true that (the) defendant spent $1 to purchase the winning lottery ticket, however the dollar spent was arguably marital money and, as such, a joint investment," Mr Mills ruled, according to the Associated Press.

Court records revealed Mrs Zelasko filed for divorce in the Oakland County Circuit Court in 2011, and the divorce was finalised in 2018.

The couple married in 2004 and share three children.

Mr Zelasko's lawyer hit back at the decision in a court document.

"Rich was lucky, but it was his luck, not Mary's, that produced the lottery proceeds," the lawyer wrote in a court filing.

The case echoes that of UK lottery winner Nigel Page, who was sensationally ordered to pay his ex-wife millions — even though she had dumped him almost a decade earlier.

Mr Page won a £56 million ($A89 million) EuroMillions jackpot in 2009 — and his ex-wife Wendy immediately sued him for a slice of the winnings, even though she had left him for another man in 2000 and taken their young daughter with her.

She originally wanted £8 million ($A14.6 million), but in the end Mr Page was ordered to hand over £2 million ($3.2 million).

Mr Page — who remarried after his win — is believed to be the first lottery-winning husband in the UK to be successfully sued for a slice of their winnings.

It was also reported the ex-wife also scored a massive increase in child maintenance payments after the lottery win, from £150 ($A275) a month to £2000 ($A3670).

One of the world's most famous unhappy lottery winners is Jane Park, who made headlines back in 2013 after pocketing £1m ($A1.8 million) in the EuroMillions jackpot.

She was just 17 at the time, and the win made her the UK's youngest-ever lottery winner.

In 2017, Ms Park famously complained her lotto win had "ruined" her life and announced she was considering taking legal action against the UK's National Lottery for negligence.

"I think 18 should be the minimum age for winning the lottery, at the least. The current age of 16 is far too young," she told Sunday People at the time.

She said her life was easier before she hit the jackpot when she earned just $A14 an hour as an administration assistant and shared a two-bedroom council flat with her mother.