In the finale of Babylon 5, we find out that John Sheridan and Delenn have a child named David, but unfortunately we never see him on screen. Given that Delenn is half-Minbari and half-Human, is David fully human? Or is he quarter-Minbari?
According to the tie-in novel Out of the Darkness, he's a quarter-Minbari but appears entirely human. Minbari women seem to find him physically appealing but largely because of his self-confidence and general attractiveness.
On the other hand, when faced with studies, David consistently rose to the occasion with such facility that his teachers wondered just how much he could accomplish if he applied himself fully.
Outwardly he appeared Human. The color of his hair had shifted over time. He had gone from being towheaded to dark-haired, and he tended to wear it long. This annoyed his father, whose old military instincts kicked in. Every so often, he would extol the virtues of a short haircut, but David seemed to pay such critiques no mind. Curiously, his eyebrows retained their light color, but the dark eyes beneath remained evocative of his mother.
He did, however, possess his father's charisma. That much was unmistakable. Nor was his charisma limited to its effects on Humans; Minbari women - grown women - would do double takes when he passed, looking him up and down appreciatively while he winked at them or came up with some bon mot that always prompted gentle laughter or looks of amusement.
As to why he wasn't seen in the show, JMS spoke to this in the audio commentary for B5: Sleeping in Light.
"The other problem being that I didn't want to show David yet. And he would be a mix of Minbari and Human and I hadn't worked out quite the look that I wanted for that yet. I also didn't want to lock us into an actor in case we see that person down the road."