Simon's mother died during childbirth after finally delivering a male heir. His father, Lord Hastings, was only concerned with the boy's ability to carry on the family name and showed no grief for his wife.
A close friend of his mother, Lady Danbury, intervened, helping Simon find his voice and gain the confidence to eventually confront his father.
Anthony Bridgerton is furious about the arrangement, distrusting Simon’s rakish reputation and fearing for his sister's honor. The Origin Story: Simon’s Past Bridgerton s01e02
On his father's deathbed, Simon vowed that the Hastings line would die with him as the ultimate act of revenge. The Subplots Bridgerton - S01E02 - Shock and Delight [Transcript]
in any room I entered. Come. You can speak. I understood you well enough. And I will help you to overcome this stammer of yours. . Scraps from the loft Bridgerton S01E02 Recap - TV Tropes When young Simon developed a stutter
The episode reveals why Simon is so determined to never marry or have children through a series of flashbacks:
By pretending to be "glued to each other's side," Simon avoids mothers looking to marry off their daughters, while Daphne becomes a "prize" coveted by other men who suddenly see her as more desirable because a Duke wants her. Bridgerton s01e02
When young Simon developed a stutter, his father rejected him as a "failure" and sent him away to be hidden from society.