How do we know that R' Yakov was a Son of Rabbi Yitzchok Eizek Katz and Toba Margulios?
According to מזכרת לגדולי אוסטרהא R' YEK only had 1 son ר' ישראל הכהן אבד"ק לעווי" and this one son had only 3 daughters
Anyone with any info?
