Was that Kevin singing in the Batman Beyond episode "Out of the Past?"
It certainly sounds like him, especially during the second song and at times during the first. I believe Kevin starred in a stage musical at one point, and he did do a little bit of singing (though in a comical way) in an episode of Rachel Gunn, so chances are it was him singing in "Out of the Past."
Is Kevin married? Does he have any childen?
At this time, he is not married and does not have any children.
Does Kevin have any siblings?
Kevin has one sister (who lives in Florida) and two brothers, one of whom is named Tom. I'm not sure who's older or younger, though.
Is Kevin still doing commercial voice overs?
According to Kevin himself, he's done several commercial voice overs while voicing Batman on the various animated series, and I know of one Gatorade commercial for sure that he did because I've heard it. He also recently did voice over for TV spots to the Warner Bros. movie Blood Diamond.
How often does Kevin return to the stage?
Most likely, he returns to the stage when he has the time. In 1998 he did Arthur Miller's The Last Yankee in New York, and I believe he was still involved with The New Batman/Superman Adventures at that time, so he appears to still do plays whenever he gets the time and the chance.
Why was Kevin's character in Tour of Duty killed off?
According to Lee Russell, military advisor for Tour of Duty, "The character of Captain Wallace had never been written as strongly as it should have been, in my opinion, and actor Kevin Conroy had been limited to some walk-on roles. He was a Principle, and was being paid a lot of money and not used. It was inevitable that he should go." Mr. Russell also added that Kevin became so bored that he took a second job in Honolulu, sketching tourists, just to have something to do every day.(Information courtesy of TourofDutyFanPage.com)
Wasn't there another Batman series called Batman: Gotham Knights?
Batman: Gotham Knights was a title often associated with the "revamped episodes" produced from 1997-1998 when they were originally going to air as their own show. But when the Kids WB! decided to pair it with Superman: The Animated Series, both shows lost their original titles, as the anthology was named The New Batman/Superman Adventures. Bruce Timm has stated that the revamped episodes were originally going to be titled The New Batman Adventures. Batman: Gotham Knights is nothing more than a title created by the fans.