I’m assuming you and your cousin did have sex. If you were a minor (under the age of 18 in most places) and your cousin was not, this could be a serious offense. You did not say whether you gave him your consent or if he forced himself on you, but in many cases a minor is “legally incapable of giving consent to a sexual act” and thus it could be labeled as “statutory rape.” You also did not tell us if your cousin has apologized to you for taking advantage of you while you were so young. That too would be good to know, for even though your question is about “forgiving yourself” he too would need to be forgiven if he was sincerely sorry for the act. You never said if you were a believer in the Lord Jesus Christ, which is important to know in order to give you a scriptural answer to your question. Not knowing all the facts, I will give you two answers: 1) What to do if you are not a believer, and 2) What to do if you are a believer.

1) If you are not a believer, I would encourage you to “believe on the Lord Jesus Christ, and you will be saved” (Acts 16:31…NKJV). Jesus Christ died for your sins on the cross so your sins could be forgiven. We read in 1st Peter 3:18, “For Christ also suffered once for sins, the just for the unjust, that He might bring us to God.” The prophet Isaiah spoke of this in Isaiah 53:5-6, “But He was wounded for our transgressions, He was bruised for our iniquities; the chastisement of our peace was upon Him, and by His stripes we are healed. All we like sheep have gone astray; we have turned, every one, to his own way; and the LORD has laid on Him the iniquity of us all.” If you take your place before God as a sinner, you can take God at His Word and believe that Christ took your place on the cross (“the just for the unjust”) and allowed your sins to be laid upon Him so He could suffer God’s judgment instead of you. The moment you believe on Christ you will be FORGIVEN! How do I know that? Because of what we read in Acts 13:38-39, “Therefore let it be known to you, brethren, that through this Man is preached to you the FORGIVENESS OF SINS; and by Him everyone who believes is JUSTIFIED OF ALL THINGS from which you could not be justified by the law of Moses.” Once you are forgiven by God of ALL YOUR SINS, you will be able to forgive yourself of any sin you have committed, for why would you not forgive yourself since God has forgiven you? And you will also be able to forgive others who have sinned against you. We see this in Ephesians 4:32, “And be kind to one another, tenderhearted, FORGIVING ONE ANOTHER, just AS GOD in Christ FORGAVE YOU.”

2) If you are already a believer, you can take to heart what I just wrote. Since God has forgiven you of all your sins, there is no reason not to forgive yourself. No matter what sin you may have committed, that sin was “laid on Christ on the cross” and He was “wounded and bruised by God for that sin.” God cannot overlook sin so He dealt with your sins at the cross. They are now gone as far as God is concerned and thus, we told in Hebrews 10:17, “And their sins and iniquities will I remember no more” (KJV). Since God “will not remember your sins” you too “should not remember your sins.”  Regarding the sin that your cousin committed against you, we saw that the believer should be “forgiving one another, just as God in Christ forgave you.” Of course, he should also be sorry for what he has done and apologize to you for it, but your heart should be ready to forgive him just as God was ready to forgive you the moment you repented of your sins and believed on the Lord Jesus Christ for forgiveness. If he is not yet a believer in Christ, you can share the good news of Jesus Christ with him so he too can experience the peace and joy that comes with being forgiven by God through Christ.  (DO)  (569.1)