What are Birth right?
Gen 25:31. The first-born son among the Jews enjoyed special privileges above his brethren, and these privileges were hence called his birthright, or his right by birth. Among these privileges were, consecration to the Lord, Ex 22:29 ("In consequence of this fact -- that God had taken the Levites from among the children of Israel, instead of all the first-born, to serve him as priests -- the first-born of the other tribes were to be redeemed at a valuation made by the priest, not exceeding five shekels, from serving God in that capacity. Num 18:15-16 comp. Luke 2:22 ff." -- Home's Introduction); great dignity, (Jon 49:3; a double portion of his father's estate, Deut 21:17; and (in the royal families) succession to the kingdom. 2 Chr 21:3. Though this was not invariably the case. Solomon was a younger son; so was Jehoahaz, 2 Kgs 23:31, Eze 23:36,- and so was Abijah. 2 Chr 11:18-22. The eldest son seems to have been regarded, in the father's absence, as in some respects his representative. The paternal blessing was also in a peculiar sense the right of the first-born, though the right itself and all the blessings of it might be forfeited or transferred, as in the case of Jacob and Esau, Gen 25:33, Reuben and Joseph. 1 Chr 5:1. But whoever enjoyed it was regarded as invested with great dignity and superiority. The Jews attached a sacred import to the title "first born." Hence the peculiar force and appropriateness of the titles "first born," "first begotten," given to the divine Redeemer. Rom 8:29; Col 1:18; Heb 1:2, Ex 6:4, 1 Chr 24:6.
Bibliography Information Schaff, Philip, Dr. "Biblical Definition for 'birth right' in Schaffs Bible Dictionary". bible-history.com - Schaff's