I have family members, as well, with many brothers and some of them having one name while some had another. I've heard that the surname of every 4th son or of some sons would be changed within Jewish families to avoid conscription into the Russian army, as Jews were conscripted for 25 years and could be taken as young as 12 and put in Cantonist schools (military schools). The goal of these schools was apparently not only to train them to become soldiers but also to convert them to Christianity. I have the names Kallner/Callner, and Frieman in my Lithuanian family (Frieman was originally Furman in this family). I have the dates of birth for all but one brother. The oldest had the last name Furman. It then goes Kallner, Frieman, Frieman, Callner, Callner, Callner, and Kallner being the surname of the son whose birthdate I don't know. Even among one of his sons, there's a mixture of Callners and Friemans.

I've also read that, unless you were married by a government official in Lithuania (which of course would have been a priest), the child would have to have the mother's surname. This doesn't work with the Kallners/Friemans, as the mother's last name was Kahn, but it may explain another side of my family.