Proverbs 17:17 describes sibling bonds with particular force: "a brother is born for adversity." The Hebrew construction — leyarah yullad ach — means a brother was brought into existence for the time of trouble, born specifically for the moment when adversity comes. The sibling is not merely a companion in ordinary life. Scripture describes them as given for the hard moments. The loss of a sibling is therefore the loss of the person designated for exactly the season you now face alone.
Psalm 88 is the only lament psalm that ends without resolution — the final line is "darkness is my closest friend." It is in the canon, which means it is a sanctioned prayer. Unresolved grief before God is not a failed prayer. It is an honest one, and God receives it. The grief of losing a sibling does not require a tidy resolution to be brought before God.
Commentary is from a charismatic Protestant perspective, drawing on KJV text and public-domain sources including Spurgeon, Andrew Murray, and Matthew Henry.