Sentence:  The first-born in every house, “from the first-born of the Pharaoh on the throne, to the first-born of the captive in the dungeon,” unaccountably found himself enlisted in the ranks of this new power, and estranged from his <WSD>natural</WSD> friends. 
Meaning of the word marked with <WSD> tags:  Connected by the ties of consanguinity.