Conditions on marriage due to suckling from same mother

Malik :: Book 30 : Hadith 30.1.4
Yahya related to me from Malik from Thawr ibn Zayd ad-Dili that Abdullah ibn Abbas said, "The milk which a child under two years old sucks, even if it is only one suck, makes the foster relatives haram."
Bukhari :: Book 3 :: Volume 48 :: Hadith 828
Narrated 'Uqba bin Al-Harith:
I married a woman and later on a woman came and said, "I suckled you both." So, I went to the Prophet (to ask him about it). He said, "How can you (keep her as a wife) when it has been said (that you were foster brother and sister)? Leave (divorce) her.