I take from it that the ones closest to Abraham are those who followed him and those who believe. It is clear, why would I take from it more than what is apparent? And what is the relation with this topic?
There is always more to a verse than what is apparent to people who read it heedlessly, since what is important is how it relates to the Surah, and relates to every verse in the Surah whether directly or indirectly, and how that Surah relates to other Surahs in Quran, and how they emphasize on the truth.
So that is one reason you ought to take more than what is apparent to you.
The other question is what it's relationship to the topic.
Indeed this Syed concept is similar to how Bani-Israel distinguished themselves for being related to Yaqoub, but Quran says:
1. Bani-Israel were selected to have the Prophets amongst them and for them to made leaders and for those leaders to be the inheritors, because of their patience and resolve in love of God. It's the same in the past, when believers were patient, God saved them from an oppressive people. It was not due to them being sons of Yaqoub.
2. The closest to Abraham were those who followed him and those who believe meaning if some person in a remote place follows Abraham but doesn't have his blood, he is closer than one who does not follow him but doesn't have his blood. This is directly linked to the issue of Syeds, because, we have no proof any of them follows Mohammad (pbuh&hf) more than a non-Syed, so no special status is really given.
3. The Quran shows every people had Prophets, I mean, is always people related to the Prophet by blood that are special and to be treated at a higher pedestal?
4. Indeed the families of Prophets ARE chosen, but what does Quran mean by that? We see example of Mariam, Yahya and Isa, we see example of Isaac, Yaqoub, Yusuf, we see example of Sarah, etc. They are pure through out their lives, and God knew they would be, and he knew they would have resolve and patience for love of God for which he made them into leaders, for their certainty in his value and beauty. There is no hint what was meant by family of Abraham or family of Imran were just pious believing people related to them by blood.
Indeed a pious person related to them by blood and pious person not related to them by blood, because Prophets relate to people as their leader and guide and people are to be spiritually from them, are the same in regards to closeness.
The Shariah would reflect that.
In the Thul-Qurba who khums was due to, were special, not every person related by blood and this emphasized and reminded with that some of holders of family relationship are closer in the book of God than others, and we see this is true of Yusuf with respect to Yaqoub for example over his other bothers.
While it makes sense if I have a son I love my son more than another person who has same level of goodness and that shouldn't be a huge factor, he is my flesh and blood, and I am not a spiritual leader or anything that people be born out of me, that my son remains close regardless if his conduct is righteous but rather if he is conduct is not righteous the love should make me want to guide him and help him....when it comes to Prophets they are special to all people, not just their blood family.
And for that reason, their true family, cannot be just normal blood or believers that happen to blood bound.