Jude 1:6 (Young's Literal Translation)
[b]messengers[/b] (angels) also, those who did not keep their own principality, but [b]did leave their proper dwelling[/b], to a judgment of a great day, in bonds everlasting, under darkness He hath kept
Jude 1:14-15 (NKJV)
14 Now Enoch, the seventh from Adam, prophesied about these men also, saying, Behold, the Lord comes with ten thousands of His saints, 15 to execute judgment on all, to convict all who are ungodly among them of all their ungodly deeds which they have committed in an ungodly way, and of all the harsh things which ungodly sinners have spoken against Him.
2 Peter 2:5 (NKJV)
4 For if God did not spare the angels who sinned, but cast them down to hell and delivered them into chains of darkness, to be reserved for judgment; 5 and did not spare the ancient world, but saved Noah, one of eight people, a preacher of righteousness, bringing in the flood on the world of the ungodly;
PERSONALLY I think speculating about the bloodline of the messiah is weird because like John the baptist said God is able to raise up children to Abraham from these stones. Also Jesus Christ is NOT of the seed of Man but John says "the Word became flesh". He was conceived by the power of the Holy Spirit in the virgin Mary - not by the power of Adam's blood, seed, etc.
The thing about the sons of Seth seems silly in my opinion. I think there was some debate a couple thousand years ago as to whether angels could actually mate with women but look at the scriptures. What do you think? Also who's Enoch and how does Jude know what he said when he's not quoted as having said that in the bible? That's in the book of Enoch which is not very popular with some people. The text may be corrupted or have had things added to it but it at least has that quote from Jude and is believed to have been written before Jesus was born of Mary. ALSO, and I think this may have a lot more to do with the suspicion people have toward it, it definitely tells the story of the angels mating with women. There is actually more to it in that book and it also goes into a story of angels who taught men to alter the world with technologies, sciences, dyes, cosmetics, etc.
What stuck out most to me is that the story of heavenly beings mating with humans and producing hybrid or whatever offspring, mighty men of renown, is identical to greek mythology. Even the resulting violence and bloodshed. Look at greek mythology, it's full of wars of so-called god's and weird mutants. Justin Martyr wrote that the greeks got their stuff from Moses who's writings were much older than theirs. So I don't know. But how many cultures have a flood story? Maybe a lot of cultures/histories contain a similar story to these wicked angels mating with humans?
Just be careful with the Enoch thing because a lot of people like to lump it together with some pretty crazy heretical stuff. The book I bought that had the translation of Enoch also contained disgusting blasphemies against Christ. So guard yourself. Remember he who thinks he stands should take heed lest he fall.
You can find translations of Enoch online.