It was an eloquent story, told with great pride by the Stamps star.
"She's quite a remarkable woman," Cornish said of mother Margaret and her love story.
A mother of five, Margaret is now married to a woman.
"People are always surprised when I tell them about my mom's situation but for me it's something I'm proud of," said Cornish, the CFL's leading rusher. "She'd been through a lot and she finally found someone that she loved and for me there's nothing more positive in the world."
Cornish says he is "pretty outspoken" when it comes to gay slurs.
"I don't like certain slurs being used and any time I hear them, I speak up," he told reporters when asked about the issue. "I think for the most part my team's pretty respectful.
"We have a lot of guys, a lot of smart people, on this team and you don't really hear too many homophobic things going on at all so it's really not something that comes up. But you know for me, I would like people to be more accepting."
After raising her kids on a music teacher's salary in New Westminster, B.C., — "She ensured we all had great educations," said Cornish — Margaret returned to school and took her master's in ethics. She then became an Anglican priest.
"That's what she wanted to achieve and for me that's been a motivation my entire life," said Cornish.
Cornish recalled coming home for Christmas break from the University of Kansas.
"She was super-excited, so I was like 'Did you meet somebody or something?' And she said 'Yeah.' And then I said 'So what's he like?' And she said 'It's a she.'
"And for me, it took maybe 15 seconds to process and then it was 'OK, that's pretty cool.' And that was that."
Cornish said people are often surprised on hearing about his mother and her partner, but are usually accepting "especially after they meet them."
Cornish's mother has returned from a holiday in Israel to see Sunday's championship game against the Toronto Argonauts.
Later in the day, Cornish was named the CFL'S Most Outstanding Canadian. In his acceptance speech, he thanked his coaches, teammates and others.
"Once again, I'd like to thank my mom — well, my two moms," he concluded. "Because who are we without our families?"
Both moms were in the audience. Later, Cornish was runner-up to Toronto's Chad Owens as Most Outstanding Player.
Cornish's father died while he was in college.
"I never knew him but I am thankful, he gave me some good genetic code," he said, drawing laughs.
Earlier, a reporter for a local gay and lesbian publication asked Stamps coach John Hufnagel if his team would be receptive to an openly gay player.
"Can he throw?" asked Hufnagel, drawing laughs. "Can he catch? Is he fast? It's a free country."
Pressed on the issue of homophobia in sport, he said: "I've never thought about it, truthfully."
Note to readers: This is a corrected story. Cornish's name was misspelled in para 19 in a previous version.