Instead of denials or accusations, he's issued a glowing statement welcoming his new daughter into the world. He is, his spokesperson says, "delighted". He "couldn't be happier and more supportive".
Hong has moved into a house in Fulham, near Grant's, and the actor has long spoken of wanting to be a father. In fulfilling this ambition, Grant has become the latest in a string of high-profile "casual fathers" - dads who may not still be with the mother of their child, but who seem to be taking to the role.
When Jude Law was named as the father of Samantha Burke's baby, the story was reported with a frenzy similar to the one that has greeted Grant's bundle of joy. Burke, a model, posed for pictures in Hello! before Law had visited.
A father of three children from his previous marriage to Sadie Frost, and now something of a playboy, his subsequent silence was greeted with a hefty dose of scepticism. But it seems Law has come good. There has been no mud-slinging, no public acrimony. The parents have come to an agreement and appear to be sticking to it.
And Benicio Del Toro, who learned of his impending fatherhood after splitting from Rod Stewart's daughter Kimberly, has been the model of responsibility.
Ideally, when it comes to Grant, the "casual" moniker will be a misleading one. "The importance of a father's role is paramount," says Andrew Watson, a parenting expert and author of Down To Earth with a Bump: The Diary of a First-Time Dad. "Studies reiterate it again and again. It affects the child's self-esteem and academic achievement.
Children with involved fathers are less likely to be associated with drugs and crime." With parents living apart, it can be difficult to obtain the right sort of relationship - but there's no reason to think it isn't possible.
Thus far, then, things look good for Grant jnr. With her father publicly committed to maintaining a role in her life and her parents on seemingly good terms, she might be destined to lead a charmed existence. Still, there are a few golden rules to follow.
"When fathering from a distance, consistency is key," Watson says. "Let your child know what to expect and stick to it. Short, regular visits are better than long and infrequent ones. When you're with them, give your undivided attention - remove any obstacles that could prevent that.
"And taking time off work to spend with them may mean there is less money in the bank for the ever-increasing bills, but it is an investment of another sort."
With Grant living just around the corner, his daughter is likely to see plenty of him - but for parents who live further apart, there are other ways to keep up relations. "Do everything you can to maintain a presence - send regular photos, Skype, pick up the phone," says Watson.
"It is a cliche, but the benefits of fatherhood are enormous. You gain a better understanding of relationships, see what the other half is like. You learn new skills. You're more engaged with the world."
- The Independent