Not only was Dinah raped by shachem at the age of 8 she also had a child from him!

One day Dinah, the daughter of Jacob and Leah, went to visit some of the Canaanite women.When Shechem son of Hamor the Hivite, who was chief of that region, saw her, HE TOOK HER AND RAPED HER. (Genesis 34:1-2)

“His soul became attached to Dinah.” At that time Dinah was eight years and one month old. Our sages (Bereshit Rabbah 72,6) arrive at this conclusion by assuming that Leah’s prayer that her fetus should be a girl was offered when she was in a state of advanced pregnancy. Dinah was born before Joseph as the Torah mentions Rachel as becoming pregnant after her birth. Joseph was born 14 years after Yaakov had arrived in Charan when Yaakov started serving Lavan an additional six years for his sheep. They stayed in Sukkot for 18 months before moving on to Shechem. This makes Joseph seven and a half years old at that time. Dinah was seven months older than he (Joseph was born at the end of a seven month pregnancy) so that made Dinah eight years and one month when she was raped. (Rabbeinu Bahya, Bereshit 34:3:1 Torah Commentary by Rabbi Bachya ben Asher, trans. Eliyahu Munk, 1998.)

Simeon’s sons: Jemuel, Jamin, Ohad, Jachin, Zohar, and Saul the son of a Canaanite woman. (Genesis 46:10)

THE SON OF THE CANAANITISH WOMAN — means the son of Dinah, who had been associated with a Canaanite (Shechem). When they (her brothers) had killed Shechem, Dinah refused to leave the city until Simeon swore to her that he would marry her and regard the child she was about to bear as his own (cf. Genesis Rabbah 80:11).

Genesis 46:10 tells us Dinah she had a son called Shaul this is also mentioned on Ellicott’s Commentary for English Readers

What does that tell you

Dinah was also given away to Shachem after Jacob found out she was raped. But her brothers killed shechem and his tribe. Notice from the above commentary simeon her brother said he would marry her?

It gets worse a different Midrash relates that Dinah was married to Job, basing this on Job’s telling his wife: “You talk as any shameless woman [ha-nevalot] might talk!” (Job 2:10), and on the episode of Dinah in Gen. 34:7: “because he had committed an outrage [nevalah] in Israel” (Gen. Rabbah 19:12). 

So now Job was married to Dinah. Now if we are to take Genesis 46:10, then it’s likely Dinah had her son when she was 9 years old from shechem and Job took her after she had the child. No doubt the son would be Shechem's, by Dinah, which son was adopted by Simeon through a marriage to his full blood sister? And Dinah is being referred to as a Canaanitess (and not by name for what reason...?) because she had been joined to the Canaanite Shechem in marriage, correct? In other words, she became a Canaanitess through that marriage. If I've understood correctly, it is an interesting find.

I've also taken Gen 34:12 to be Shechem's proposal to take Dinah as a wife, v.15 to be the conditions the brothers would allow that (circumcision), v.24 the fulfillment of the conditions, and v.26 confirmation that the brothers had in fact given Dinah to be Shechem's wife, since she was taken from his house three days (v.25) after the circumcision event--which implies to me that on the day of circumcision Shechem took her to his house as his wife. So while she was violated initially, I don't see anything to indicate she was also not married to him for those three days. 

If the "Canaanite" here is Dinah, who married Shimon (see Bereshit Raba 80, 10), it is possible that Shaul isn't Shimon's son, but rather a son born to Dinah from Shechem. If so, even this son did not estrange himself from Jacob's family. She is called "Canaanite" because her son, biologically, was the son of a Canaanite (man). Therefore we can conclude that even then, when a daughter of Jacob marries a Canaanite, the newborn's identity is considered based on his/her mother (see Yevamot 45b).

And some say that Job lived in the days of Jacob and that he married Dina, the daughter of Jacob. As it is written here: “You speak as one of the loathsome women speaks” (Job 2:10), and it is written there in the account of the incident involving Dina: “He has done a loathsome act in Israel” (Genesis 34:7). (Bava Batra 15b:7)

So we can conclude Dinah was raped when she was 8 years old, had a son called Saul. Soon after Job married her rebuked her when he was angry (Job 2:10) rejecting the fact she was an 8 year old girl who was raped. Also one wonders If the punishment for raping a young girl is paying 50 shekels to the father and marrying the raped girl (Deuteronomy 22:28-29). Why then did Jacobs sons kill shachems when he raped their 8 year old sister? 

One must also note that, Jacob had no problem giving away his 8 year old daughter for marriage. There is no evidence where Jacob objected the handover of Dinah to Shechem. It’s understood traditionally a father gave away his daughter at a very young age. We also see the two brothers of Dinah did not object her age. It was their rage and anger that that make them kill Shechem and his tribe. Why didn’t the father or brothers say our daughter/sister is extremely young for marriage?

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Jacob hides 7-8 year old daughter Dinah from his brother Esau to prevent him from  marrying her

That same night he arose, and taking his two wives, his two maidservants, and his eleven children, he crossed the ford of the Jabbok. (Genesis 32:23)

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ואת אחד עשר ילדיו AND HIS ELEVEN CHILDREN — But where was Dinah? He placed her in a chest and locked her in so that Esau should not set his fancy upon her (desire to marry her). On this account Jacob was punished — because he had kept her away from his brother for she might have led him back to the right path; she therefore fell into the power of Shechem (Genesis Rabbah 76:9). (Rashi commentary)

Bereshit Rabbah 76,9 raises the question of where Dinah was in all this, and answers that Yaakov had put her into a box that he had locked. His concern had been that if Esau would see her he would take her by force. "Moreover, if Esau had indeed married Dinah she would not have been raped by Shechem."(Radak commentary )

Besides, on his return to Palestine, when he was preparing to meet his brother, he concealed his daughter Dinah in a chest, lest Esau desire to have her for wife, and he be obliged to give her to him. (Legends of the Jews  1:6:215)

As soon as the messengers came and said to him : WE CAME UNTO YOUR BROTHER ESAU, Jacob took Dinah and put her in a chest so that Esau would not see her and take her for a wife. Gen. R. 76:9.(Midrash Tanchuma Buber, Vayishlach 19:2)

Secondly, he was punished for denying Esau a glimpse of Dinah, for maybe she could have exercised a beneficial influence on him if he had married her. (Rabbeinu Bahya, Bereshit 34:1:1)

At least all Talmudic opinions agree that it was theoretically permitted to marry a stepfather's wife (excepting the mother), and to marry a stepsibling (a man marrying his stepsister, etc. (Yebamot (Tosefta) 2:3)