Hadiths are surely a very important resource to understand Quran. However, above argument is totally made on purpose. Because people who claim this, know very well that the word “âbâ” in Quran means “fathers” which indicates both your father and your father’s father and so on to all upper generations.
Allah commands: “Do not marry with whom your fathers married (…)” in the verse 4:22. This includes women whom their fathers married and whom their grandfathers married. According to this verse, wife of grandfather is also in the forbidden list. This is explained in the same way in books of Islamic Jurisprudence. For example, Al-Ikhtiyâr which is one of the essential books of Hanafi sect, has the following information about this subject:
Women, whom their fathers or grandfathers had divorced are unlawful to the sons and grandsons, regardless of how high the generation gap is. Because Allah commands: “Do not marry with whom your fathers married, except what has already occurred (…)” (4:22)
Neglecting the integrity between Quran and hadiths has caused a lot of misunderstanding and trouble. Considering the hadiths as “unrecorded revelation” (wahy ghayr al-matluw), declaring Quran and hadiths as two different sources and giving priority to hadiths over Quran is the worst of it.
 Al-Ikhtiyar li Ta’leeli’l-Mukhtar, vol.3, p.85.