Since all of the speaker's mother's offspring are unmarried, the speaker is unmarried. Mira's mother-in-law is the mother of Mira's husband. The statement says Mira's husband's grandmother is the speaker's grandmother. This implies Mira's husband's mother is the speaker's aunt. Therefore, Mira's husband is the speaker's cousin (aunt's son). Thus, Mira is the wife of the speaker's aunt's son.