Bert said Jaime had stayed with their family over Christmas at the family home in Whangarei.
"She came up here and is a lovely young kid, a wonderful kid. She cooked some beautiful food, we went out boating, she fitted in like a daughter." They had been seeing each other for a few months.
"I wish her well and hope it works out well for her."
Bert said he had met Jaime's mother Sally and understood why she took such an active role in her daughter's life.
"[Sally] has had to take on the father role as well. She has had a pretty tough life at times by the look of it. And it's good to see some happiness come their way. If it happens with Sonny then she should go for it."
Rowsell's brother-in-law and Black Sticks linchpin Phil Burrows took to Twitter to defend Dwayne Rowsell.
"@SonnyBWilliams #stolemybrosgirl #cold," he tweeted.
He then replied to teammate Simon Child's tweet about bad traffic by saying: "hahaha at least @SonnyBWilliams didnt steal ur mrs".
Child replied: "Yeah that's s***s sad man."
Jaime was pictured with mother Sally at Sonny Bill's sparring session on Friday in Hamilton. Williams is preparing to fight Clarence Tillman III.