Because Jacob crossed his blessed hands, Ephraim, the second son, became the eldest son and got the birthright. According to the whole Bible, birthright includes dual land, king's office and priest's office.
Although Israel is the eldest son of God, it lost its birthright because of unbelief. In the New Testament, the birthright was transferred from Israel to the church. The church is made up of sinners who have been redeemed and reborn. In the church, we are a group of people born under the name of the eldest son. This firstborn name gives us the right to fully enjoy Christ, become a priest of God, and take power with Christ. The road to birthright is faith. As long as we call on the name of the Lord Jesus and accept him as our savior, we will become the eldest son of God and enjoy all the riches of Christ.