My kinsfolk have failed - My neighbors (קרובי qârôbāy), those who were near to me. It may refer to "nearness" of affinity, friendship, or residence. The essential idea is that of "nearness" - whether by blood, affection, or vicinity. In Psalm 38:11, it denotes near friends.
And my familiar friends - Those who knew me - מידעי myudā‛ay. The allusion is to those who were "intimately" acquainted with him, or who were his bosom friends.

My kinsfolk have failed - Literally, departed: they have all left my house, now there is no more hope of gain.

My kinsfolk have failed,.... Or "ceased" (a), not to be, or that they were dead, which is sometimes the sense of the word; but they ceased from visiting him, or doing any good office for him; those that were "near" (b) him, as the word used signifies; that were near him in relation, and were often near him in place, in his own house, in company and conversation with him, now ceased to be near him in affection; or to come nigh him, to converse with him and comfort him, and sympathize with him, which might be expected from persons nearly related:
and my familiar friends have forgotten me; such as were well known to him, and he to them, and who not long ago were very loving and friendly to him, and very freely and familiarly conversed with him; but now they forgot him; the friendship that subsisted between them, the friendliness with which they had visited him, and the favours they had received from him; they so slighted and neglected him, that it seemed as if he was forgotten, as a dead man, out of mind; or as if they did not remember that there ever was, or at least that there now was, such a man in the world as Job: these could not be true friends; for "a friend loves at all times, and a brother is born for adversity", Proverbs 17:17; a real friend loves, and continues to love, in adversity as well as in prosperity; and such an one, who sometimes sticks closer to a man than a brother, is born and designed to be of service to him in a time of trouble; but so it was ordered by divine Providence, and according to the will of God, that Job should meet with such treatment from his brethren, relations, acquaintance, and familiar friends, for the trial of his faith and patience.
(a) "desierunt", Pagninus, Montanus, Vatablus, Mercerus, Drusius, Piscator, Schmidt, Michaelis; "cessant", Schultens. (b) "propinqui mei", Pagninus, Montanus, &c.