So, I did it. I caved and started designing an older Oscar Barrett (based mostly on his actors William and Henry Deutschendorf and Sigourney Weaver).
He was probably born in very early 1989/very late 1988 according to the film’s timeline so he’s a bit younger than Callie. It’s been theorised that his (biological) father was the violinist from Ghostbusters II, but Ivan Reitman said in 2016 that he thinks Venkman is the father. Do what you will with that information.
But yeah, I haven’t gotten around to PROPER designs yet because I still haven’t got his personality and life details quite figured yet. All the canon information we really have about him is that he did martial arts (which is probably a reference to his actors being martial arts champions) so I’ve got way too much creative license here. Leave your thoughts if you have any I’d be interested in suggestions.