Because all those children share one same nature of flesh and blood, Jesus likewise had to share this nature. This is why his death destroyed the one holding the power of death, that is the devil, and freed those who remained in bondage all their lifetime because of the fear of death.
Jesus came to take by the hand not the angels but the human race. So he had to be like his brothers and sisters in every respect, in order to be the High Priest faithful to God and merciful to them, a priest able to ask pardon and atone for their sins. Having been tested through suffering, he is able to help those who are tested.
Second Reading: Heb 2:14-18