Inserted into the Israelite genealogy is the parenthetical lineage of those descended from Esau, the brother of Jacob. Esau is the 22nd generation from Adam but is not in the lineage of Jesus.
There are no answers to the 4 questions that I record in my journal, but Esau's information is given in both Genesis chapter 36 and here in the latter portion of I Chronicles 1. I believe this is meant to show a parallel: a compare and contrast of sorts, between the families of the twin brothers, Esau and Jacob, or Israel as he was renamed by God.
The genealogy of Esau's descendants reads easily enough in verses 35-37 and by comparing these verses with verse 39 and Genesis chapter 36 we can place each person in their proper place in the family tree given earlier in I Chronicles 1.
24. Zephi (Zepho)
24. Kenaz and Timna*
Genesis 32:3 tells us that Esau made his home in the land of Seir which later became known as the country of Edom. It was to the land of Seir that Jacob sent messengers stating that he, Jacob, was coming to see Esau. Remember that the last time Jacob interacted with Esau was when he, Jacob, had tricked their father, Isaac, into giving Esau's blessing to Jacob. Now Jacob feared Esau so he sent an emissary before him requesting forgiveness and peace. It was that very night as Jacob camped after hearing from his messenger that Esau was coming to meet him with 400 men that the Angel (most likely a pre-incarnate appearance of Jesus) wrestled with Jacob, wounded him (therefore making him weaker right before the big meeting with Esau!), and changed his name from Jacob (which means "cheater") to Israel (which means "God strives").
Why then was the name of Seir included in I Chronicles 1:38? A good clue is found in the name that I have highlighted in blue above. Timna was the concubine of Kenaz, Esau's grandson. Seir was Timna's father which explains how Mount Seir became the land of Edom. Esau's family married into Seir's family. See Genesis 36:12, 22 to view Timna's place in the history of Edom.
We have the records both here and in Genesis 36 of how this land was ruled in the years prior to the kingdom years of Israel. Ironically, it may have been jealousy over the kingdom of Edom, Esau's land, that made Israel's descendants demand a king of their own! They did not seem to grasp that their relatives relied upon depraved humanity to rule in justice while they themselves had God, the Supreme Ruler of the universe as their King.
We do not know where Seir fits into the "big picture" on Noah's family tree but since many of the branches end much earlier than that of Esau's family tree Seir could have been descended from either Shem, Ham, or Japheth. The only reason we know anything about him at all is because his family intermarried with Esau's family and were therefore distantly related to the Hebrews.
1. Seir (where Esau relocated after he left Isaac was known as Mt. Seir)
3. Hori (whose descendants were known as the Horites)
2. Timna (female, the concubine of Kenaz, the grandson of Esau)