Modern translations of Mat 19:29 that are based upon the best current reconstruction of the original Greek New Testament (UBS4) are all consistent with the wording in the NRSV:

And everyone who has left houses or brothers or sisters or father or mother or children or fields, for my name's sake, will receive a hundredfold, and will inherit eternal life.

The KJV and other translations based upon the so-called Textus Receptus (TR) Greek text add "or wife" after "mother." The NJKV reads:

And everyone who has left houses or brothers or sisters or father or mother or wife or children or lands, for My name's sake, shall receive a hundredfold, and inherit eternal life.

The corruptions in the TR, KJV, and NKJV are explained briefly at http://www.bibletexts.com/verses/v-mat.htm#mat1929. Below are three points that explain why "or wife" was not only not in the original text of Mat 19:29 but also why it was not in the original text of Mar 10:29 and Luk 18:29.

(1) MAR 10:29 - It is the dominant conclusion of biblical scholars that the Greek texts of Mat 19:29 and Luk 18:29 were based on the Greek text of Mar 10:29. It therefore should be emphasized that Mar 10:29 has no viable manuscript evidence for "or wife" (Greek: e gunaika) as being part of the text. The writers of Matthew and Luke, both of whom consulted the Gospel of Mark, published their gospels about 10 or 20 years after the Gospel of Mark was published. This means that the source for both Mat 19:29 and Luk 18:29 did not include "or wife;" therefore, we should expect to find that the original text of Mat 19:29 and Luk 18:29 also should not have included "or wife." This is exactly the conclusion that is reached below under the heading of "(3) ANTE-NICENE FATHERS."

(Scholars generally date Matthew and Luke around 80-90 A.D. and Mark around 70 A.D., though a date of 50 A.D. for Mark and for a papyrus fragment thereof has also been proposed. [More info.])

(2) 1CO 7:10-11 - 15 to 20 years before the Gospel of Mark was published, Paul quoted Jesus as saying:

A wife must not leave her husband; but if she does, she must remain single or else be reconciled to her husband; and a husband must not divorce his wife. (1Co 7:10-11)

This directly coincides with Mark's later account of Jesus' teaching in Mar 10:6-9. Paul went on to offer his own opinion:

If a Christian man has a wife who is an unbeliever and she agrees to go on living with him, he must not divorce her. And if a Christian woman is married to a man who is an unbeliever and he agrees to go on living with her, she must not divorce him. For the unbelieving husband is made acceptable to God by being united to his wife, and the unbelieving wife is made acceptable to God by being united to her Christian husband. If this were not so, their children would be like pagan children; but as it is, they are acceptable to God. However, if the one who is not a believer wishes to leave the Christian partner, let it be so. In such cases the Christian partner, whether husband or wife, is free to act. God has called you to live in peace. How can you be sure, Christian wife, that you will not save your husband? Or how can you be sure, Christian husband, that you will not save your wife?(1Co 7:12-16, TEV)

(3) ANTE-NICENE FATHERS - Around 180 A.D., Irenaeus (130-202 A.D.) (Against Heresies) quoted what appears to be an earlier version of Luk 18:29,30:

Whosoever shall have left lands, or houses, or parents, or brethren, or children because of me, he shall receive in this world an hundredfold, and in that to come he shall inherit eternal life. (ANF 1:562)

"Or wife" was not included in Irenaeus' quote of Jesus. Around 195 A.D. Clement of Alexandria (150-215 A.D.) (The Stromata, or Miscellanies) quoted Jesus from Mat 19:29:

The Lord says in the Gospel, "Whosoever shall leave father, or mother, or brethren," and so forth, "for the sake of the Gospel and my name," he is blessed... (ANF 2:412)

Both Irenaeus and Clement of Alexandria did not include "or wife."

I have checked the entire Ante-Nicene Fathers and all New Testament apocrypha, including the Nag Hammadi writings. The only other similar quotes are all from Cyprian (?-258 A.D.), where around 250 A.D. he quoted from Luk 18:29,30:

There is no man that hath left house, or land, or parents, or brethren, or sisters, or wife, or children, for the kingdom of God's sake, who shall not receive seven-fold more in this present time, and in the world to come life everlasting." (The Epistles of Cyprian, ANF Vol 5:348; The Treatises of Cyprian, ANF 5:440, 506, 538)

The fact is that the wording of Irenaeus and Cyprian are both most similar to Luk 18:29,30, except that Irenaeus did not include "or wife" - nor did Clement of Alexandria in his quote from Mat 19:29. This leads to the conclusion that the original version of Luk 18:29 also did not include "or wife" but that "or wife" was added to a text of Luke 18:29 sometime during the 70 years between the time of Irenaeus and Cyprian (between 180-250 A.D.) Then sometime between the time of Clement of Alexandria and Cyprian (between 195-250 A.D.), "or wife" began to be added to some texts of Mark and Matthew, assimilating the wording that had begun to be added to Luke sometime between 180-250 A.D.

To explore "Divorce - What were the genuine teachings of Jesus and other early Christians?," see http://www.bibletexts.com/terms/divorce.htm.