Mark: While Berkeley was doing Outland, he once did a strip where Steve visits Opus after being gone (i.e not in the strip) for a long time. During this visit, Steve reveals that since last time, he got married and had a kid.
Incidentally, he then can't shut up about the kid, as he suffers from the "new father syndrome". When Opus tries to change subject while asking if Mandela's made any progress in South Africa (strip being made in the 90s, after all), Steve replies "You know, if Mandela had been bald, white, and 70 years younger, he'd look just like my son."
Hope that clears things up for you, Mark.