The Old Testament features extremes of sibling rivalry. Cain murders Abel. Joseph's brothers sell him into slavery. Jacob, Joseph's father, and his brother Esau, are lifelong rivals. Jesus' disciples, brothers James and John, fight over who will be Jesus' closest confidant when he achieves political power (their goal, not his.)
There are romantic triangles galore. Abraham's wife Sarah at first cannot have a child so she gives him to her servant, the concubine Hagar; yet when Hagar produces Abraham's son, Ishmael, Sarah is so jealous that she nags Abraham until he abandons Hagar and Ishmael in the desert. Abraham's grandson, Jacob, is tricked into marrying the sister, Leah, whom he's NOT in love with, and later after he marries Rachel, his love, the two sisters vie with each other in producing his children (along with the children produced by his other wives.) King David conspires to have a close friend die in battle so he can marry his friend's wife.
There's incest. When Lot settles in a solitary area without any eligible men, his daughters get him drunk two nights in a row so each one can lie with him (without his knowledge) to get pregnant and carry on the family line. There's forcible incest: King David's daughter Tamar is raped by one of her half-brothers. Absalom, her full brother, is so enraged that his father does nothing to punish the rapist that he eventually tries to violently overthrow his father. David survives as King, but as a broken man - Absalom dies in battle.
There is grief. David mourns for Absalom. Mothers mourn for their dead children and cannot be comforted.
There are two messages in the Bible for today's families. The first is that human nature and families do not change and never will. Tragedies still abound. Marriages are sometimes loveless and many men today have serial wives and separate families with wives and former wives fighting to get the father's attention to help raise the children they've sired. Parents make mistakes while parenting. Siblings fight and betray each other. Incest and rape still happen.
But the Bible's other message to families is that God still loves and cares for every member of every family, no matter what mistakes and what sins they've committed. God remains healer, counselor, friend. When we read these stories and see what flawed personalities the great patriarchs and matriarchs of the Bible had - and yet they were loved and guided by God - this can give us hope! No matter how sinful or wrong-headed these men and women were, they prayed and God heard their prayers. God gave them strength to survive and grow.
Cain murders his brother, yet a merciful God decrees that no one should kill Cain in revenge. God appears to the servant and concubine Hagar, driven into the desert with her baby, and tenderly promises her that she and her son will live. Joseph's brothers eventually repent and ask Joseph for forgiveness. King David repents for conspiring to have his friend killed and begs God to be merciful; after Absalom's death, he becomes a humble man. In fact, mercy is the name of God in the Bible. No matter how messed up a family is, the Bible takes the long view and demonstrates that God cares for everyone and brings peace and justice in the long run.
"Like the families of Scripture, our own families are shaped by stories of difficulty and persistence....Christian parents are right to look to Scripture for guidance. But Scripture does not provide us a Handbook on how to do parenting right. Instead, it presents us with a God who works through the complications of human experience. Our own families certainly participate in their own levels of complexity and drama. We should be comforted that Scripture tells us the story of a God that has done great things through challenging circumstances." (Jake Kohlhaas, "Family Bible Study," "America" magazine, June 20-27, 2016.)