Itzchak Stern - Who were his parents?

Being from Petrova, it seems that he was the son of Mordechai Stern https://www.geni.com/family-tree/index/6000000006951686640, the only Stern in Petrova.

I therefore plan to move his and his brother's Chaim profiles to link to Mordechai. If you have any information points to Mendel Shmuel being his father I would very much appreciate hearing about it.