Thanks to the team for providing the list of chapters (63, 241, 329) to explain the circumstances. I forgot that it wasn't just Lin Hong's father who died because of the Emperor; Yuning's mother also died because of him.
@Trueflame001
He's probably the eunuch mentioned in chapter 63. Lin Hong's father criticized his role during the campaign against the northern barbarians, which earned him the eunuch's and/or his masters' animosity and got him killed.