Quoting Commentary for II Samuel 15:34

ואלה בני צבעון ואיה וענה, “and these were the sons of Tzivon, Aiah and Anah.” The letters ו in front of these names are merely prefixes and have nothing to do with the names of these two people. We find something parallel in Samuel Ii 15,34 עבד אביך ואני מאז which means “I have been a servant of your father from way before.” In this verse we are told that Anah was a son of Tzivon, whereas from verse 20 it is clear that both Anah and Tzivon were brothers, sons of Seir HaChori. In order to ensure that we would not think that the Anah mentioned was the uncle of the other Anah, the Torah added that the Anah mentioned here was the one who discovered the mules in the desert.
Our sages in Pessachim 54 explained that we are dealing with the same Anah who had been mentioned previously and that he had been sired through his father having slept with his mother. The reason the Torah lists him here as one of the sons of Seir HaChori is because all the people of his generation thought that he was the son of Seir HaChori. The Torah, however, was concerned with relating his true ancestry. The Torah mentions him as either himself crossbreeding a donkey with a mare or discovering the products of such crossbreeding, to illustrate how illegitimate sexual relations between human beings result eventually in bastardy or association with animals which were the product of such crossbreeding. At the time it was considered very astute of Anah to have discovered or crossbred two such species of animals.
According to the opinion of Onkelos who translated the verse as Anah having found גבריה, “men in the desert,” the word ימים must be understood as a variant of אימים, antediluvian giants. According to Onkelos the plain meaning of our verse is that Anah was met or attacked by members of that people who wanted to rob him of the donkeys belonging to Tzivon which he was minding. The Torah reports that although alone, Anah managed to save the donkeys from the hands of these אימים. Nachmanides interprets the verse in this fashion.

AND THESE ARE THE CHILDREN OF ZIBEON: AND AJAH, AND ANAH. The letter vav in the word v’ayah — (and Ajah) is redundant. Similarly: Thy father’s servant ‘va’ani’ (and I) have been in time past, so ‘va’ani’ (and I) will now be thy servant.²⁹⁰II Samuel 15:34. In both cases the vav is redundant, and the meaning of the word is ani (I). And there were the heads of their fathers’ houses: ‘va’epher’ (and Epher), and Ishi²⁹¹I Chronicles 5:24. — here too the vav is redundant. And there are many others like them.
Now this Zibeon was the third son of Se’ir the Horite,²⁹²Verse 20 here. and he begot these two children, Ajah and Anah, and Scripture relates that this Anah, Zibeon’s son, was that same Anah who found the mules in the desert as he fed the asses of Zibeon his father, to differentiate between him and his uncle Anah,²⁹²Verse 20 here. the brother of his father, Zibeon. This Anah, Zibeon’s son, was Esau’s father-in-law.²⁹³Verse 2: Oholibamah the daughter of Anah.