It was from an heir-hunting company called Finders International, which had been tasked with tracking down Ross's next of kin.
Initially, the company believed Ross's estate to be worth a mere $A10,000 (NZ$10,600) — but after investigating further, it was revealed the 80-year-old had a bank account containing more than $A280,000 (NZ$297,000) thanks to a lucky lottery syndicate win.
He ended up splitting the inheritance with his 24-year-old sister, meaning they scored around $A140,000 (NZ$148,000) each from a man they didn't even know.
Christou told the Eastern Daily Press the surreal situation had been a welcome shock.
"This entire episode has been life changing, not least in the unexpected cash but in closing a painful chapter in my family's history," he said.
"My mum never discussed my grandfather so we went our entire lives to date thinking we didn't have one.
"Having lost our mum due to complications with her battle with alcohol and drugs, we feel our grandad and mum are smiling on us kids through this positive outcome. We have further discovered that our grandad did try to connect with us through our mum over the years, and that shows his positive intention."
Nick Christou - pictured with wife Karen - initially thought he was being scammed. Photo / Facebook
Christou and his wife Karen, 43, married seven years ago and have since gone on a belated honeymoon to Las Vegas with part of the inheritance.
The father of four told The Mirror he also used the money to pay down debt, buy a car and bike and bulk up his savings.
"I felt a bit numb at first, to be honest. I let it sink in, and I thought this could change our lives as a family," he told the publication.
"I have to pinch myself now. The whole thing has been a rollercoaster ride.
"My advice to other people following our experience is to be inquisitive about your family — know who they are. It could just change your life forever."
Finders International founder Danny Curran told the UK media his job was a rewarding one.
"The best part of probate research, or heir hunting, is what we uncover, and how family members react when they're connected after years apart of contrasting lives," he told the Eastern Daily Press.
"Nick Christou's story proves the importance of trying to at least know members of your family, even if fallouts have occurred.
"Personally, for me, it's fantastic to see younger beneficiaries for a change. In the case of Nick and his sister, both in their 20s and 30s — a real boost in life for them both."
