My great grandmother Rebecca Schoenberg had 3 brothers- Yomtov, Jacob Leib, & Hyman (Chaim). Their father was Mordechai (Max) & his brother was also Jacob Leib Schoenberg. Yomtov changed his names to Jacob as well. So yes- it’s possible. Not sure why my great Uncle Yomtov also chose Jacob but he did.
Perhaps one of yours also had a different name but went by Abraham? Have you found their gravestones? Yomtov/Jacob’s gravestone lists his name as Yomtov on the grave. I would look at their gravestones to see what they say & if they both list them as being “the son of” the same man to verify that they are indeed full brothers.
Best of luck!
BLUMENTHAL: Russia> Poland> NYC> Rochester, NY
SCHOENBERG/SHOENBERG: Russia/Ukraine (Kuz’myn) (Satanov)> Rochester, NY
POLLACK/POLLAK: Russia/Ukraine (Kuz’myn) (Satanov)
COHEN/ha COHEN: Russia/Ukraine (Kuz’myn) (Satanov)
GRYNGRAS: Poland (Radzilow) (Szczuczyn)