Judge Farish told the court the girls were aged only 12 and 13 or 14 when Kelly committed the offending aged 17.
Kelly kissed the youngest girl before touching her on the breast, after which the girl got up and left.
He then tried to touch the older girl beneath her clothing, threatening her not to tell anyone what had happened or he would hurt a family member.
Later, when Kelly realised the threat had worked, he waited around the church where he met the girls and raped her in a park.
The woman who was raped told the court she severely cut herself by writing the word "whore" on her thigh after being deeply impacted by the incident.
"He stole some of the most important years of my life from me, and I will never get them back," the woman said.
It has also been revealed Kelly has jailed in 2016 for procuring a woman to commit sexual violation by oral sex on a boy aged 15-months.
Where to get help:
• If it's an emergency and you feel that you or someone else is at risk, call 111.
• If you've ever experienced sexual assault or abuse and need to talk to someone call the confidential crisis helpline Safe to Talk on: 0800 044 334 or text 4334.
• Alternatively contact your local police station
• If you have been abused, remember it's not your fault.