This happened a few years ago.  I was working late in my office one evening. 
Knock Knock. 
One of the female employees, Lorraine, working for me was outside my office.  I asked her to come in and sit down. 
I asked Lorraine what she wanted to discuss with me.  She said “I think you know I am getting married next week.  I also sent you the invitation.”  I acknowledged receiving the invitation and said my wife and I will be there. 
Lorraine said she wanted me to do her a big favor/help. 
I asked her if she is short of money and I will loan her some money.  Or, if she wants extra days off to go on honeymoon, I will consider giving her extra days off. 
She said she did not want any of them.  After I asked her 3 times what she wants, she asked me if I can give her away during the wedding. 
Just an example,  This is not me or Lorraine.
A father walking his daughter down the aisle and giving her away to the groom is a well-accepted and sometimes touching part of the ceremony.  If the bride has no father or father has refused, then a brother or uncle will take his place. 
I asked her what happened to her father or brother or uncle.  She said they all refused because this is her third marriage. And, she started to cry.  I said I will think about it and let her know the next day. 
I called Lorraine into my office the next day and told her I would give her away, but with one condition.  I told her this should be her last marriage.  No more marriages for her.  She accepted.  (As far as I know, she is still married to that guy.) 
On the day of wedding, I asked my wife if she is coming.  Originally, she was planning to come.  When she came to know I am going to give away the bride, my wife decided not to come to the wedding. 
My wife said:  Go ahead and give your sister away.  Enjoy the free food and drinks. 
That is what I did.