Who was Hophni's brother?

Hophni's brother was Phinehas. According to 1 Samuel 1:3 and 2:34, Hophni and Phinehas were the two sons of Eli the priest who served at the tabernacle in Shiloh. Both brothers are consistently mentioned together throughout the narrative in 1 Samuel 1-4.

Hophni and Phinehas are described as "worthless men" (1 Samuel 2:12) who abused their priestly office. They took portions of the sacrifices beyond what was permitted (1 Samuel 2:13-17) and engaged in immoral conduct at the entrance to the tent of meeting (1 Samuel 2:22). Despite Eli's warnings, they refused to listen. God sent a prophecy through a man of God (1 Samuel 2:27-36) and later through the young Samuel (1 Samuel 3:11-14) that both sons would die on the same day as a sign of judgment. This was fulfilled in 1 Samuel 4:11, when both Hophni and Phinehas were killed in battle against the Philistines, and the Ark of the Covenant was captured.

The other names belong to different biblical lineages. Nadab and Abihu were sons of Aaron who died offering unauthorized fire before the Lord (Leviticus 10:1-2). Eleazar was another son of Aaron who succeeded him as high priest. Abinadab appears in several contexts, including as a son of Jesse (David's brother) and as the man in whose house the Ark was kept at Kiriath-jearim.