Recently there has been several postings on this site with questions regarding the signatures on marriages held at the meeting houses. I finally went through some of my "stuff" I had set aside, to review for a later date, and found what may answer that question. This comes from Heritage Books Archives Quaker Marriage Certificates by Gwen Boyer Bjorkman, 1991, CD-ROM. "The underlined names are witnesses and the third column was for bride, groom, parents, and family." So, as I look at a list from Concord MM, 1742, there are 3 columns. It appears that friends and witnesses signed on the first two columns and bride and groom, parents and family signed on the third column. It does not show ages of anyone, so I would say that everyone present had their name on this document to show they were in attendance and approved of the wedding. I don't know how many had to be witnesses, but on this paper it varied and witnesses were on all three lines. It also appears that the groom was the first person on the third column, then the bride (bride using surname of new husband), then father of bride, mother of bride, father and mother of groom, then family. This was in 1742, so I'm not sure this is true to this day, but thought you would be interested and it may help you with older searches of ancestors marriages.