Damian's Prank
At this point in the story, most of the Bats are ignoring Dick or neutral but not contacting Dick regularly. The only one who still sees Dick is Damian at this point.
Damian goes to visit Dick about a week after he gets married. Damian doesn't see anything crazy about Dick being married suddenly because the League of Assassins has arranged marriages and unions for the benefit of the league regularly. Once he meets her, Damian does evaluate whether Stevie is a beneficial match for Dick. She passes his inspection.
Over the next couple of months, Stevie bonds with Damian, becoming a maternal, nurturing presence in his life. He calls her Stephanie.
Damian decides to prank his family, as well as the world, by keeping them from finding out unless they actually talk to and see Dick. He does this by letting them think that the Stephanie that Dick communicates with or talks about is Stephanie Brown, who is neutral/not mad about Spiral and they bonded with when Dick was Batman.
This lasts for a while (a few months) because of Damian manipulating them, as well as asking Stephanie B. and Dick to do certain things, and them trusting him. Optionally, Stephanie B. finds out and enthusiastically joins in. Clark, Barry, and Diana also know (they’re still close to Dick); Clark and Barry keep the secret after insistence from Damian. Diana is away on a mission. Once the prank is revealed, Dick is extremely proud of Damian. Everyone else is shocked by the prank and Dick being married.