Here are 2 Bible verses about brother and sister relationships from the Old and New Testaments of the Holy Bible (King James Version), sorted from most to least relevant.
John 3:16-17 KJV
For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. For God sent not his Son into the world to condemn the world; but that the world through him might be saved.
Matthew 13:55-56 KJV
Is not this the carpenter’s son? is not his mother called Mary? and his brethren, James, and Joses, and Simon, and Judas? And his sisters, are they not all with us? Whence then hath this man all these things?