What is the significance of "Yesomim Hayinu v'Ein Av"?
Rav Sadya Gaon: We were like orphans without a father.
Ibn Ezra: We were with the Gerim 1 like orphans without a known father. Normally, the father's family helps his orphans.
Ri Kara: We have a father! However, the father cannot help his sons, and they cannot help their father. Therefore, we are like orphans without a father. "Imoseinu k'Almanos" supports this (refer to 5:3:2:1).
Palgei Mayim: We are living orphans (i.e. their father is alive) - our Father in Shamayim departed from us.
Torah Temimah citing Eichah Rabah: Hashem said, you cried "Yesomim Hayinu v'Ein Av" - the redeemer that I will establish for you in Madai will not have a father or mother! It says about Esther "Ki Ein Lah Av va'Em" (Esther 2:7).
Magihah (in Toras Chayim): I.e. the strangers who took our Nachalah.
Why does it say "Imoseinu k'Almanos"?
Ri Kara: They are like widows, because their husbands cannot feed them.
Palgei Mayim: Our mothers are Tziyon and Yerushalayim. (Their Husband departed.)