This is more geared towards relationship advice and I have posted on different subreddits to get the best advice possible.

My sister Lily(fake name)is not only my sister, but my best friend as well.She is beautiful,kind,intelligent,and very likable.She does charity work like helping our church on food drives and volunteering at a soup kitchen for the homeless.She did something very wrong, but I believe she is a good person.My brother Luke(fake name) is not biologically related to me or the rest of our family, but that doesn't really matter.7 years ago my mom's best friends(Luke's biological parents) died in an automobile accident and our family decided to adopt him.Regardless of genetics Luke is my brother and I love him and care for hm.

In short I caught my sister molesting my younger brother Luke.This has apparently been going on for months and my sister begged me not to tell my parents.However after long thought,prayer,and posting to r/changemyview I decided to tell my parents.

My parents freaked out and kicked Lily out.Even though I begged them not to they went to the police.I called Lily and she told me that she understood why I told our parents and that she still loves me and Luke.My parents saw that I was contacting Lily and they forbade me from contacting her.They told me that they love Lily in spite of what she did and they know that I love Lily.However, what Lily did was wrong and we have to cut off contact with Lily and perhaps in the future we can reconnect with her and bring her back into the family.

My brother is in therapy right now and my parents came and asked me if I wanted to see a therapist.I told them no because not only do I not need it, but I don't want to divert any attention Luke can get.My sister is my rock.She is always there for advice and whenever I'm trouble.I trust her,love her,and care for her.Not being able to talk to her and offer support in a time where she is going through so much is killing me.After all Lily always supported me through my troubles.

I keep pleading with my parents to let me contact her, but they are firm in their decision to not let me contact her.I keep second guessing my decision to tell my parents because not only do I miss not having my sister, the consequences she face may be enormous.

My parents are Presbyterian so I wanted to form a Christian argument to why they should allow me to have contact with my sister again and that's why I'm here.

Does anybody have any advice on what I should say to my parents for this to work?

It means that you need to decide who you care about more: your younger brother, or your younger brother's RAPIST. Have you even considered how your behaviour is impacting on your brother?

If you love him as much as your sister you should show it, and stop trying to keep this connection to his abuser. You are HURTING your family and they will resent you for it in the end, if they don't already.

You need to grow up and realise that your sister is not the person you thought she was. She's a child abuser and the fact that you're choosing this abuser over your brother is astonishing to me.

You seem to be incapable of recognising that what you're doing is actively harmful. You NEED therapy. And the fact that you're constantly posting this on different subreddits and deleting it when you don't get the validation you want shows that deep down you know this is wrong. PLEASE, get therapy. Your choices now could affect your entire future with your family.

If it comes down to my brother or my sister.......Well I won't lie, I'll choose my sister even though what she did was wrong.

Yes,my sister is a child abuser, but does that mean I should stop loving her?

Also I'm not harming anybody right now.I just want to talk to her on the occasion.My brother will never know.How am I hurting anybody by talking to my sister?

Wow. WOW. You will choose to support a pedophile over her victim. This is absolutely abhorrent on every level, and trying to hide behind your faith will not work.
You ARE harming people - your parents are dealing with what your sister did, trying to make sure this doesn't ruin your brother's life and ON TOP OF THAT you're trying to force them into accepting this continued contact with the person who has caused all this in the first place! This is undoubtedly causing harm, and you're trying to justify that to make yourself feel better. You are an incredibly selfish person.

Actually maybe you should move out and stay in contact with your brother's rapist, you sound like you deserve each other.

I'm sorry, but I won't stop loving my sister.If Jesus loved and forgave humanity for our sins shouldn't I at the very least attempt to be like Jesus and love my sister?