Muhammad Bin Saaib Al Kalbi narrates in his book (Al Salabah Fe Ma'rifat Al Sahabah) (3/212)
Nufayl was working for Kalb Bin Luayy Bin Ghalib AlQarshy and
he (Kalb) died. His new master was Abdul Muttalib, Sahak was also
working for Abdul Mutalib she was shepherd taking care of his sheep.
He separated between them in the pasture and they agreed one day to
meet in a rest home. Nufayl desired and loved her. Abdul Muttalib had
made her put on pants of leather with a lock on and he kept its key
with him to her status of him. When he (Nufayl) chased her she said:
nothing from what you are saying is for me and he has made me put
this leather and put a lock on it. He said: I can trick him, he took
some butter from the sheep's buttermilk and smeared the leather and
what is around it of her body with the butter till slipped down to
her thighs. He did effect her and she got pregnant by him with Al
Khattab. When she had given birth to him she threw him on some
garbage during the night with fear of Abdul Muttalib. A Jewish woman
named Jenazah picked up Al Khattab and raised him. When he grew up he
used to cut wood and was named 'Al Hattab' the wood cutter. So with
the letter 'Ha' but was distorted in the vocabulary. Sahak was faring
him in secrecy, one day he saw her and her bottom was lowered. He
didn't know who she was, he fell on her and she got pregnant by him
with Hantamah. When she had given birth to her she threw her in the
dumps outside of Makkah. Hisham Bin Magheer Bin Walid picked her up and
raised her and she was attributed to him. When she grew up and Al
Khattab frequently visited Hisham and he saw Hantamah and liked her. He
asked Hisham if he could marry her and Hisham allowed her to marry
him. She gave birth to Omar. Al Khattab was Omar's father because he
and Hantamah got married and she gave birth to him. And at the same
time his grandfather because he and Sahak got Hantamah. Al khattab and
Hantamah are from the same mother Sahak.
Nufayl + Sahak = Al Khattab
Al Khattab + Sahak = Hantamah
Al Khattab + Hantamah = Omar
We see that Hantamah is the mother and sister of Omar Bin Al Khattab i.e. she is the wife and the daughter of Al Khattab.
And Al Khattab is his father because he is Sahak's lover (i.e. who committed fornication with her) and her son at the same time. I.e. he is Omar's father and grandfather at the same time.
Sahak is his grandmother, mother of his father and the mistress of his father at the same time.
Al Salabah Fe Ma'rifat Al Sahabah (3/212)
Ilzam Al Nawasib. By : Nurullah Zarihi.