Sailu's mother is the daughter of Kalyan's sister. How is Kalyan's mother related to Sailu's mother?

Pointing towards a woman, Amit said, "She is the sister of my wife's husband." How is the woman related to Amit?

Vimal is the son of Mikka, and Nina is the daughter of Milan. Milan is the sister of Mikka. Who is Milan to Vimal? 

M is the son of P. Q is the granddaughter of O who is the husband of P. How is M related to O? 

If P is the husband of Q and R is the mother of S and Q. How is R related to P?

Pointing to a girl in a photograph, Sunita said, "She is the mother of Renu, whose father is my son". How is she(Sunita) related to that girl?

Vikas showed a photograph and said: “She is the daughter of my grandfather’s only son.” What is the relation of Vikas with the girl in photograph?