Mike Tindall's grandmother was "dead against" him marrying Zara Phillips.
The 41-year-old rugby star met the 39-year-old equestrian - who is the daughter of Princess Anne and her ex-husband Captain Mark Philips - in 2003 and though they went on to wed in 2011, the sportsman's elderly relative was concerned their marriage would be "shunned" because of Tindall's humble background.
• Memoir reveals Prince couldn't stand Ed Sheeran, Katy Perry
• Memoir throws light on Prince's sadness
• Daniela Elser: Royal family's subtle dig at Prince Harry
• What would Prince want? Two years later, his estate is a mess and his legacy unclear
Mike's father, Philip Tindall, said: "He started playing for England in 2000 and it wasn't too long before he met and moved in with Zara.
"Linda's mum was dead against it. In her day, royalty married royalty and she thought the wedding would be shunned."
Philip and his wife Linda found Zara's family to be very welcoming and they spent a lot of time together during Mike's playing days.
He added: "But right from the start the whole family was just lovely.
"We'd go on a Friday night to watch the match and stop over. Sometimes we'd all go out for lunch with Zara's mum on Sunday before we went home. We spent quite a bit of time with her dad too.
"[Prince] Harry would often be round watching the rugby, so, slowly and quietly, we got to meet them all - and that's how it went on for quite a few years."
Philip thinks Mike and Zara - who have daughters Mia, 6, and Lena, 2, together - are a "fantastic team" and they're all thankful they can lead normal lives because the Olympian's parents opted not to give her a royal title.
He told the Sunday Times magazine: "Linda's mum died before she could meet Zara, but I know she'd have loved her as much as we do because she and Mike are perfect for each other. What one starts, the other finishes; they are a fantastic team.
"Zara always says she's so pleased she wasn't given a title because they've been able to live their own lives.
"They have quite a number of really good friends - people they can be sure of. Mike's friends are also Zara's friends. They're people they trust and rely on completely."