Those women with whom nikaah is permissible

Marrying a girl who was engaged to one's cousin

Q: There is a girl whom my cousin was previously in love with. The whole family knew and since he was still studying, the family wanted to marry them once my cousin's studies were over. After a year, for some family reasons, my cousin left the girl. I know that girl and I want to  marry her and she too wants the same. When my parents and the girl's parent came to know about this, they are telling us that this is not possible, my cousin won't like it, what other people will say, what elders will say etc. In my point of view, its more society and culture thinking. I wanted to know what Islam says about this? What is the view?

Marrying the stepmother's daughter

Q: Please first understand the whole story then give me an answer. My sister is married to my uncle (father's brother’s brother in-law). Before my uncle died my uncle and my father announced the engagement of his daughter with me, after few days my uncle died. As few years have passed, my grandfather decided that my father will marry my aunt and they got married. Now around 12 years have passed and my aunt is forcing me to get married to her daughter and my father has also agreed. Can I marry my step sister which is not from my father?

Marrying one's stepfather's daughter

Q: My friend Zaid's father Bakr died long back so his mother Fathima married another man Haamid. Now Haamid was also married before and his wife Ruqayyah died. In short both Fathima and Haamid are widow. This man Haamid had one daughter Aaisha with his first wife Ruqayyah. Now my friend zaid is going to marry this girl Aaisha. Is this marrage valid or haram?