Why in the Genesis, it's strongly said that Jacob and Rachel were Cousins?

Question

We read from the Torah, Bereishit 29:10:

וַיְהִ֡י כַּֽאֲשֶׁר֩ רָאָ֨ה יַֽעֲקֹ֜ב אֶת־רָחֵ֗ל בַּת־לָבָן֙ אֲחִ֣י אִמּ֔וֹ וְאֶת־צֹ֥אן לָבָ֖ן אֲחִ֣י אִמּ֑וֹ וַיִּגַּ֣שׁ יַֽעֲקֹ֗ב וַיָּ֤גֶל אֶת־הָאֶ֨בֶן֙ מֵעַל֙ פִּ֣י הַבְּאֵ֔ר וַיַּ֕שְׁקְ אֶת־צֹ֥אן לָבָ֖ן אֲחִ֥י אִמּֽוֹ:

And the corresponding in english:

10 And it came to pass, when Jacob saw Rachel, the daughter of Laban, his mother's brother and the sheep of Laban, his mother's brother, that Jacob drew near and rolled the rock off the mouth of the well, and he watered the sheep of Laban, his mother's brother.

When I've seen this (this week's parashah), I wondered why to repeat so many times the fact that Jacob's mother(Rebeca)'s brother is Rachel's father.

Answer 1

The Ohr HaChaim and the Rabbeinu Bachaye explain the point which is essentially to clarify the motivations of Yaakov in helping Rochel.

OHR HACHAIM

ויהי כאשר ראה יעקב את רחל, It was when Jacob saw Rachel, etc. The reason that the Torah repeats three times that Laban was the brother of Jacob's mother is to emphasise that everything Jacob did was only because Laban was his mother's brother and he tried to honour his mother by carrying out her instructions. Another reason for the Torah to repeat this information was so that bystanders who observed Jacob- a recently arrived total stranger- doing Rachel such a great favour (removal of the stone on the well) would know that he was motivated only by family considerations. This is why Jacob spelled out his reasons and as soon as he laid eyes on Rachel he mentioned that she was the daughter of Laban who was his mother's brother. This is also why he displayed concern about the flocks of his uncle. When he kissed Rachel he did not repeat this statement since he had already made plain that Rachel was his cousin. Besides, the very fact that he started crying was explanation enough that he had come face to face with a relative.

RABBEINU BACHAYE . ויהי כאשר ראה יעקב, “it happened that as soon as Yaakov looked, etc.” We find that in this verse the Torah repeats the expression אחי אמו, “brother of his (Yaakov) mother” repeatedly. This is partly in order to explain why Yaakov was so concerned with helping to water the flocks as he had pity on Rachel, Lavan’s daughter. Whatever Yaakov did, whatever feat of strength he performed, he did not perform for the sake of Lavan but for the sake of his mother Rivkah. This is why every time the Torah had to mention the name of wicked Lavan, it contrasts him with his sister, Yaakov’s mother. Yaakov remembered his mother who had advised him to go to Lavan. There is yet another reason for the repeated mention of the words אחי אמו, brother of his mother.” Whenever a person hears or sees an object he desires, he is suddenly capable of performing tasks which he cannot perform in order to secure something which his heart does not covet. The reader of this passage could be forgiven if he had thought that seeing Yaakov was taken with Rachel’s beauty he desired her physically and this is what gave him the strength to move the rock single-handedly. The Torah refers time and again to the fact that Lavan was the brother of Yaakov’s mother in order to make us aware that physical passion had nothing to do with Yaakov’s sudden burst of strength in moving the rock. The Torah was so concerned not to create the impression that Yaakov’s sudden burst of strength was inspired by passion that instead of writing: “as soon as Yaakov set eyes on Rachel he rolled the rock, etc.,” The Torah wrote instead (in a somewhat clumsy style) ”it was when Yaakov saw Rachel the daughter of Lavan, the brother of his mother, and the flock of Lavan the brother of his mother, Yaakov approached and rolled the rock etc.”

Answer 2

Genesis 28:

1 So Isaac called for Jacob and blessed him. Then he commanded him: “Do not marry a Canaanite woman. 2 Go at once to Paddan Aram, to the house of your mother’s father Bethuel. Take a wife for yourself there, from among the daughters of Laban, your mother’s brother.

Isaac commanded Jacob to find a daughter of Laban to marry.

Genesis 29:

10 And it came to pass, when Jacob saw Rachel, the daughter of Laban, his mother's brother and the sheep of Laban, his mother's brother, that Jacob drew near and rolled the rock off the mouth of the well, and he watered the sheep of Laban, his mother's brother.

Now Jacob had found one. The expression "Laban, his mother's brother" is repeated 3 times in this 1 verse. This emphasis on long-lost relatives continues:

12And Jacob told Rachel that he was her father’s kinsman, and that he was Rebekah’s son, and she ran and told her father.

13 As soon as Laban heard the news about Jacob, his sister’s son, he ran to meet him and embraced him and kissed him and brought him to his house. Jacob told Laban all these things, 14and Laban said to him, “Surely you are my bone and my flesh!” And he stayed with him a month.

In this passage, there is an emphasis, even an over-emphasis of long-distance relatives being united. Modern people have lost some of this sympathy towards ones' relatives.

Why in Genesis, it's strongly said that Jacob and Rachel were Cousins?

First, it emphasizes the fulfillment of the wish of Isaac. Second, it depicts the joyful feelings of meeting long-distance relatives for the first time. Third, it demonstrates that blood is thicker than water. All these are in contrast to the sorry affair of Esau marrying unrelated Canaanite women.