Ali (ra) married Faatimah (ra), and she was his cousin (pbuh)'s daughter.
The Prophet (pbuh) is also reported to have proposed to Abu Taalib for his hand in marriage to Umm Haani in the days before Prophethood.
Cousins are non-mahrams and veil is to be observed.
Btw, i've come to learn after studying Arabic a little myself that hijaab actually means screen as in veil and not just headscarf, although the ruling the headscarf is stronger than that of the veil - depending on the situation and circumstances, i was just watching "the golden child" and just the face of that fit woman was enough to rivet my attention and difficult to keep looking down, omg that is one bone lifter.
(11)Chapter: The characteristics of Iblis (Satan) and his soldiers(11)
)باب صِفَةِ إِبْلِيسَ وَجُنُودِهِوَقَالَ مُجَاهِدٌ: {يُقْذَفُونَ** يُرْمَوْنَ.*{دُحُورًا** مَطْرُودِينَ.*{وَاصِبٌ** دَائِمٌ.*وَقَالَ ابْنُ عَبَّاسٍ: {مَدْحُورًا** مَطْرُودًا يُقَالُ: {مَرِيدًا** مُتَمَرِّدًا. بَتَّكَهُ قَطَّعَهُ.*{وَاسْتَفْزِزْ** اسْتَخِفَّ.*{بِخَيْلِكَ** الْفُرْسَانُ. وَالرَّجْلُ الرَّجَّالَةُ وَاحِدُهَا رَاجِلٌ مِثْلُ صَاحِبٍ وَصَحْبٍ، وَتَاجِرٍ وَتَجْرٍ، {لأَحْتَنِكَنَّ** لأَسْتَأْصِلَنَّ.*{قَرِينٌ** شَيْطَانٌ.Narrated Sa`d bin Abi Waqqas:
Once `Umar asked the leave to see Allah's Messenger
(ﷺ) in whose company there were some Quraishi women who were talking to him and asking him for more financial support raising their voices.
When `Umar asked permission to enter the women got up (quickly) hurrying to screen themselves. When Allah's Messenger (ﷺ) admitted `Umar, Allah's Messenger (ﷺ) was smiling,
`Umar asked, "O Allah's Messenger (ﷺ)! May Allah keep you in happiness always."
Allah's Messenger (ﷺ) said, "I am astonished at these women who were with me. As soon as they heard your voice, they hastened to screen themselves."
`Umar said, "O Allah's Apostle! You have more right to be feared by them."
Then he addressed (those women) saying, "O enemies of your own souls! Do you fear me and not Allah's Messenger (ﷺ) ?"
They replied. "Yes, for you are a fearful and fierce man as compared with Allah's Messenger (ﷺ)."
On that Allah's Messenger (ﷺ) said (to `Umar), "By Him in Whose Hands my life is, whenever Satan sees you taking a path, he follows a path other than yours.
."حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا يَعْقُوبُ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا أَبِي، عَنْ صَالِحٍ، عَنِ ابْنِ شِهَابٍ، قَالَ أَخْبَرَنِي عَبْدُ الْحَمِيدِ بْنُ عَبْدِ الرَّحْمَنِ بْنِ زَيْدٍ، أَنَّ مُحَمَّدَ بْنَ سَعْدِ بْنِ أَبِي وَقَّاصٍ، أَخْبَرَهُ أَنَّ أَبَاهُ سَعْدَ بْنَ أَبِي وَقَّاصٍ قَالَ اسْتَأْذَنَ عُمَرُ عَلَى رَسُولِ اللَّهِ صلى الله عليه وسلم، وَعِنْدَهُ نِسَاءٌ مِنْ قُرَيْشٍ يُكَلِّمْنَهُ وَيَسْتَكْثِرْنَهُ، عَالِيَةً أَصْوَاتُهُنَّ، فَلَمَّا اسْتَأْذَنَ عُمَرُ، قُمْنَ يَبْتَدِرْنَ الْحِجَابَ، فَأَذِنَ لَهُ رَسُولُ اللَّهِ صلى الله عليه وسلم، وَرَسُولُ اللَّهِ صلى الله عليه وسلم يَضْحَكُ، فَقَالَ عُمَرُ أَضْحَكَ اللَّهُ سِنَّكَ يَا رَسُولَ اللَّهِ. قَالَ " عَجِبْتُ مِنْ هَؤُلاَءِ اللاَّتِي كُنَّ عِنْدِي، فَلَمَّا سَمِعْنَ صَوْتَكَ ابْتَدَرْنَ الْحِجَابَ ". قَالَ عُمَرُ فَأَنْتَ يَا رَسُولَ اللَّهِ كُنْتَ أَحَقَّ أَنْ يَهَبْنَ. ثُمَّ قَالَ أَىْ عَدُوَّاتِ أَنْفُسِهِنَّ، أَتَهَبْنَنِي وَلاَ تَهَبْنَ رَسُولَ اللَّهِ صلى الله عليه وسلم قُلْنَ نَعَمْ، أَنْتَ أَفَظُّ وَأَغْلَظُ مِنْ رَسُولِ اللَّهِ صلى الله عليه وسلم. قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " وَالَّذِي نَفْسِي بِيَدِهِ مَا لَقِيَكَ الشَّيْطَانُ قَطُّ سَالِكًا فَجًّا إِلاَّ سَلَكَ فَجًّا غَيْرَ فَجِّكَ ".
reference*:*Sahih al-Bukhari 3294
In-book reference*:*Book 59, Hadith 103
USC-MSA web (English) reference*: Vol. 4, Book 54, Hadith 515**(deprecated numbering scheme)
Taking the above into account along with the fact that the face veil is not applicable turing tawaf of Ka'bah during pilgrimage, it is possible say that the head covering and body shape obscuring is an absolute essential for the noble female who has reached or is reaching age, but that the face covering can be relaxed in places and circumstances where it is safe to do so - i.e where there is no fear of moving the hearts of males and especially those in whose hearts is a disease - and fear of being unrecognized by the mahram or children in busy places where it is easy to lose each other, and Allah knows best.