A $1.35 billion lottery winner is suing the mother of his child, saying she told his family about the money

• The winner of January's massive $1.35 billion Mega Millions lottery is suing the mother of his child.
• He's accused her of telling his family about the win, court documents show.

The winner of a massive $1.35 billion lottery prize is seeking damages from the mother of his child, who he says revealed the win to his family, court filings show.

The man, named only as "John Doe" in the lawsuit, beat stupendous odds to win the Mega Millions prize in the Maine State Lottery in January.

As the fourth-largest lottery win in US history, the jackpot caused a major stir.

After taxes, the lump-sum prize — from a ticket bought at a Maine gas station — amounted to just under $500 million.

The winner has sought to keep his anonymity from the outset.

According to court documents filed on Tuesday, and seen by Insider, it appears that his win was even kept secret from most of his family.

The documents show he sought to protect his anonymity with a non-disclosure agreement between him and the mother of his child back in February.

The lawsuit says that the woman, named as "Sara Smith," signed an NDA saying she must keep the jackpot a secret until June 1, 2032, when their daughter comes of age.

Business Insider was unable to contact the mother. The plaintiff's lawyer declined to provide comment to The Daily Beast, which first reported the story.

If the mother did — by accident or deliberately — spill the beans before that point, she'd have to tell him within 24 hours, the NDA said.

But, according to the lawsuit, the woman then told his family anyway. It says she got on the phone and told his father and stepmother — which soon led to several other people, including his sister, finding out.

The plaintiff is now asking her to reveal exactly who else she's told — with a penalty of at least $100,000 for each time she broke the NDA.

Lottery winners are frequently advised to stay anonymous and to set up elaborate protections to keep word from getting out. A surprising minority keep the information even from their nearest and dearest.

Andy Carter, who works as an advisor for winners of the UK's National Lottery, told Business Insider that some winners — particularly if they have marital problems — even keep it from their spouses.

But that anonymity is difficult to maintain for really big winners: "If you've won one million, it's easier to hide than a hundred million," he said.