The grieving sister of Caleb Flynn’s slain wife ripped the “American Idol” alum and ex-pastor at his sentencing Monday for putting on a phony, God-fearing facade while “living an entirely different life behind closed doors” – which culminated in the cold-blooded murder of her beloved sibling.

Kayla Keyt slammed “the man I used to call my brother” for betraying her family and fracturing their church community during a gut-wrenching victim impact statement delivered moments before Flynn, 40, was sentenced to life in prison without the possibility of parole for fatally shooting his wife, Ashley.

“When Ashley died and we learned that you were responsible, we were as shocked as anyone,” Keyt said.

“We trusted you, we believed in you, we honestly would have laid down our lives for you. And because of that, one of my greatest fears was that people would look at you and what you had done and begin questioning whether any of this – Christianity, faith, Jesus – was real,” continued the sister, who appeared calm and composed while reading her statement.

According to Keyt, children within their Christian church community have lived in a constant state of fear ever since Ashley, 37, was found executed in her bed in the early hours of Feb. 16, while her and Flynn’s two daughters – then 9 and 11 years old – were just feet away inside of another room.

“It would absolutely break Ashley’s heart to know that an entire group of children in Tipp City…have now experienced such fear, that some of them still run to their parents’ bedroom in the morning, making sure that no one broke in and shot their mother,” the sister revealed during Flynn’s Monday sentencing hearing.

“You shattered the innocence of so many children – many of them having to learn the words murder, affair, burglary for the first time,” she continued.

Flynn was found guilty of aggravated murder, felonious assault and tampering with evidence after lying to police about an intruder breaking into the family home and fatally shooting his wife while he was in another room.

Prosecutors argued that Flynn m𝑢rdєred Ashley because he wanted to start a new life with his longtime mistress, Aleigha Botner, who met the father of two as a 20-year-old intern at the same church where he was a music pastor.

Botner, now 24, sobbed while testifying last month about her and Flynn’s illicit romance – which even saw them exchange harrowing text messages about wanting to 𝘬iᩚll Ashley.

During her statement, Keyt slammed Flynn for making the family, including his grieving daughters, go through a highly-publicized trial instead of fessing up to the heinous crime.

“For months, our family prayed that you would confess and own up to all of your actions, but you didn’t. Instead, you chose to drag us through a nationally-televised trial.

“And now, the grotesque things that happened to Ashley and the evil and vile things that you said about her and our family are permanently public,” Keyt said, adding that his daughters may someday “discover details about the worst night of their lives” on the Internet.

The girls, who are now living with Keyt and her husband, “lost their mother, their father, and pretty much everything they ever owned except the clothes on their backs all in one night” – and they will carry that pain for the rest of their lives, she continued.

Just the other day, one of them “was laying beside me, sobbing into my shoulder as they both often do, because she missed her mommy and could not understand how her own father could have done this to all of us,” Keyt recalled.

Still, the sister said she forgives Flynn and his mistress.

“I do forgive you. I’ve forgiven both you and Alleigha – not because what happened should ever be excused or forgotten, and certainly not because there shouldn’t be severe consequences,” Keyt said while staring in Flynn’s direction.

“I forgive you because I refuse to allow what you did to destroy another part of my life by filling my heart with hatred and bitterness.

“I serve a God who is both merciful and just,” Keyt said. “Justice is not mine to carry, but forgiveness is.”

Later during the hearing, Keyt’s husband read heart-wrenching statements penned by Flynn’s daughters aloud in court – one of whom blasted her dad for sinning “big time” by having an affair with a “dirty girl,” while the other vowed to never visit him in prison.

Flynn frequently sobbed throughout the hearing, including while he read a lengthy statement lamenting not being able to raise his daughters and apologizing for breaking his wedding vows.

Still, the convicted 𝘬iᩚller maintained that he didn’t murder Ashley.

“I did not 𝘬iᩚll my wife…I will continue to fight for my innocence as long as the Lord allows me to,” he told the courtroom.