I am become a stranger unto my brethren - That is, They treat me as they would a stranger; as one in whom they have no interest, and whom they regard with no friendship. Compare the notes at Psalms 31:11.
And an alien unto my mother’s children - A foreigner; one of another tribe or nation; one to whom they were bound by no tie of relationship. The allusion in the language “unto my mother’s children” is intended to denote the most intimate relationship. In families where a man had many wives, as was common among the Hebrews, the nearest relationship would be denoted by being of the same “mother” rather than of the same “father.” See the notes at Psalms 50:20. The same thing occurs also where polygamy is not practiced, in cases where a man has married more wives than one. The idea of the psalmist here, therefore, is, that his nearest relatives treated him as if he were a stranger and a foreigner. Compare Job 19:13-19.