ANSWER: At least seven people in the Bible have committed suicide. Abimelech, one of Israel's Judges, took his own life after he was severely wounded by a huge millstone hitting his head (Judges 9:52 - 54). Samson famously sacrificed his life in order to bring destruction on the Philistine leadership (Judges 16:30). King Saul and his armor bearer committed suicide after Israel lost a battle to the Philistines (1Samuel 31:4 - 5).
King Zimri, ruler over Israel for only seven days, committed suicide when the people rebelled against him. He killed himself by burning his palace to the ground (1Kings 16:8 - 18). Ahithophel was a trusted confidant of Absalom (King David's son). He ended his life by hanging himself when his counsel was rejected (2Samuel 17:23). Judas Iscariot, the only recorded suicide in the New Testament, "hanged himself" (a likely reference to stabbing himself with a knife) after betraying Christ.
The greatest overlooked suicide in Scripture, however, occurred with Lucifer and one third of all the righteous angels. They killed themselves spiritually when they decided to rebel against God and willed to forever be his enemy.
The act of killing oneself is a very sorrowful event. It is especially hurtful to those who know the person and even much more the family. BibleStudy.org offers its condolences regarding your brother's death.
The world looks upon suicide in a twisted manner. People tend to categorize sin but the Bible does not! James said if you keep all of God's Law and break one little point you are guilty of breaking all of it (James 2:10). According to Jesus Christ himself, if you just have a THOUGHT in your mind with hatred toward your brother you are guilty of murder (Matthew 5:21 - 22). Hating yourself, therefore, is murder, and a breaking of the sixth commandment (Exodus 20:13).
Suicide is murder of oneself and is a sin, but it is not the unpardonable sin. The Apostle Paul states, in the book of Romans, that all of us have sinned and therefore all of us have the death penalty upon us (Romans 3:22 - 23). Whether it is suicide or some other act, all humanity stands guilty before the Eternal. Your brother did that which is common to man (1Corinthians 10:13) and therefore is no worse a sinner than the rest of us. God promises that if we confess our sins he is MORE THAN willing to forgive us and cleanse us of all unrighteousness.
The ultimate hope for your brother, and countless individuals like him who committed suicide, is the second resurrection of the dead. This is a time when God will bring back to life all those who never fully understood his truth and repented of their sins. It is a time when countless billions will have their minds opened and given the opportunity to receive eternal salvation.