There is an ancient Jewish custom for every wedding ceremony to include individuals appointed to serve as the "shoshvinin". The word "shoshvinin" is actually somewhat mysterious and of uncertain meaning. Some commentators suggest that the word "shoshvin" means "friendship". It is also used in scripture to mean "a beloved friend". In the Talmud it is used as a term to describe the monetary wedding gifts which are given by the guests in order to help offset the costs of the wedding feast. Those who partake of the wedding feast are also called shoshvinin. One who receives shoshvinim money for one's wedding is expected to reciprocate with a similar amount of money when that person gets married. One who does not reciprocate shoshvinin gifts can be compelled to do so by a Beit Din.
Other sources seem to suggest that the word shoshvinin is actually an acronym for the words "sasson v'simcha bein chatan v'kalla (happiness and celebration between the groom and the bride.)" The word shoshvinin is translated and used today in a number of contexts, including: "the best man", "the groomsmen", and "attendants". The groom's attendants are also intended to recall that just as a king is not to be seen without his attendants and entourage, neither is a groom.
The idea for having shoshvinin derives from none other than God Himself who served as the shoshvinin for Eve, bringing her to Adam. From here one should learn by example that it is not beneath the dignity of anyone to serve the needs of a bride and groom in any way which might be needed. The shoshvinin should always position themselves to the side of the bride and groom.
The groom's shoshvinin should be the ones to dress him in the kittel before the wedding ceremony. Among the reasons for this is that it further recalls the similarity between a king and a groom. Just as a king is always dressed by his assistants, so is a groom on his wedding day. It is also said to instill in a groom feelings of repentance and reminds him of the day of death. It is best that only married individuals serve as the shoshvinin.
Today, the primary role of the shoshvinin is to accompany the groom and bride to the chuppa. As such, four individuals are usually appointed as shoshvinin, two for the bride and two for the groom. The shoshvinin are typically the parents of the bride and the groom, though there are number of other possibilities and combinations which are permitted, as well. In some communities the parents walk their children to the chuppa, while in other communities the two fathers escort the groom and the two mothers escort the bride. It seems that there was once a custom to appoint elders or sages to serve as the shoshvinin. It is interesting to note that in the event of a dispute between the families as to who should walk the bride and groom to the chuppa, it is suggested that one follow the custom which the majority of one's guests are likely to follow!
As the chuppa structure represents the Jewish home, the groom is led to the chuppa first so that he will be there to welcome his bride into the home they will now build together. Similarly, Adam was created first in order that he would be able to welcome his wife, Eve, into the world. We are told that the angels Michael and Gavriel were Adam's shoshvinin. It is taught that the receiving of the Torah at Mount Sinai was an experience which was intended to be reminiscent of a wedding. God, the groom, was waiting on Mount Sinai as Moshe led the Jewish people, the bride, to the mountain. The tablets of the Ten Commandments were God's shoshvinin.
 Maharsha Eruvin 18, cited in "Bishvilei Haparasha" by Rabbi Elyakim Devorkis
 Rashi;Yevamot 63a, cited in "Bishvilei Haparasha" by Rabbi Elyakim Devorkis
 Bava Batra 144b, 145a, Rambam Zechiya U'matana 7:1
 Rambam Zechiya U'matana 7:1
 Rambam Zechiya U'matana 7:2
 Rambam Zechiya U'matana 7:2-5
 Maharash M'lublin;Chaye Sara, cited in "Bishvilei Haparasha" by Rabbi Elyakim Devorkis
 Pirkei D’rabbi Eliezer 17. See also: Minhag Yisrael Torah O.C. 239:4, Berachot 54b
 Bereishit 2:22, Berachot 61a, Eruvin 18b
 Kitzur Shulchan Aruch 147:4
 Sefer Matamim 136
 Kitzur Shulchan Aruch 147:4
 Nitei Gavriel;Nisuin 14:11
 Zohar 1:49. There are authorities who oppose this practice claiming that it is derived from Gentile customs. Shevet Halevi 3:187
 Kitzur Shulchan Aruch 147:5
 Rema Y.D. 391:3
 Be'er Moshe 2:165, cited in "Bishvilei Haparasha" by Rabbi Elyakim Devorkis
 Based on Devarim 22:16
 Bereishit Rabba 8:13
 Pirkei D'rabbi Eliezer 41
 Tanchuma;Ekev 10, Shemot Rabba 41:6