When Joseph told his second dream to his family, his brothers didn't believe the dream would come true. However, the Bible says Joseph's father wondered what the dreams meant. In other words, Jacob most likely believed Joseph's dream was from God, and therefore reflected the truth. Otherwise, why would Joseph spend time pondering its meaning.
"This time he told the dream to his father
as well as to his brothers,
but his father scolded him.
'What kind of dream is that? he asked.
'Will your mother and I and your brothers
actually come and bow to the ground before you?'
But while his brothers were jealous of Joseph,
his father wondered what the dreams meant."
Genesis 37:10-11 (NLT)
However, soon after Joseph has these two dreams, Joseph's brothers plotted to kill him. They sold Joseph into slavery and sent Joseph's coat dipped in goat's blood to their father. Jacob recognized the coat immediately, and believed without question his beloved son was torn to pieces by a wild animal. The Bible says Jacob grieved deeply for his son for a long time.
"Their father recognized it immediately.
'Yes,' he said, 'It is my son's robe.
A wild animal must have eaten him.
Joseph has clearly been torn to pieces!'
Then Jacob tore his clothes and dressed himself in burlap.
He mourned deeply for his son for a long time.
'I will go to my grave mourning for my son,'
he would say, and then he would weep."
Genesis 37:33-35 (NLT)
God gave Joseph two dreams just before he was taken from his father Jacob. The last dream was revealed to Jacob by his son Joseph. Jacob pondered the meaning of this dream, but when he was shown Joseph's coat covered in blood soon after, Jacob gave no more attention to its meaning. God had forewarn Jacob though Joseph's dream that He had a future plan for Joseph, but Jacob refused to believe. Instead, Jacob readily believed his son Joseph was dead when he saw only a coat covered in blood, not Joseph's body. As a result of Jacob's unbelief in God, Jacob mourned deeply and lengthily. Jacob had a choice to make, and he choose to believe indirect evidence, instead of direct evidence from an all-mighty and all-knowing God. This resulted in great sadness for Jacob.