It’s all but certain that the Dominating Sect Master’s unborn baby was killed during the attack years ago, but I wish the comic had acknowledged it, especially since they ended up forming an alliance with the ones that did it.
Hell, the child could have died from something else, but since we’ve never seen them and they’re never mentioned since that attack, the implication is that attack is what did it.
Of course, it’s possible the kid is alive and kicking, but it would be weird for that to be the case with no mention of them, especially since Seol would have spent years around them and playing with them if they were alive.