ואלה שמות בני ישראל (שמות א:א)

When Reb Berl Karniol z’’l of Lemberg was blessed with a baby boy, he sent a telegram to Maran Reb Yisocher Dov of Belz zt’’l, asking which name he should give the child: Yitzchak, after his father, R’ Yitzchak Korniel z’’l, or Yehoshua, after his father-in-law, R’ Yehoshua Rubinfeld z’’l. He added that he personally preferred the name Yehoshua.

Maran replied that he should specifically name the child Yitzchak. Later, when Reb Berl was blessed with another son, he named him Yehoshua. When Yehoshua reached marriageable age, he married the daughter of Reb Yitzchak Cohen z’’l.

Only then was it understood why Maran had instructed that the elder son be named Yitzchak. Had the firstborn been named Yehoshua, the second son would have been named Yitzchak, which would have created a difficulty with the shidduch. In Belz, they are careful—following the will of Reb Yehuda HaChasid zt’’l—that a chassan and his mechutan should not share the same name.