Jonatan is engaged to Sandra, but she is not engaged to him. They didn't want just one of them being the active partner, leaving the other passive, so both have to propose. She has to do it before October (this discussion took place in 2016 - last year, that is).
Why before October?
Jonatan is a game community member. The year before this (in 2015, counting correctly) the yearly meetup was in a castle in Scotland, and one of his friends, G., was forced to be the witness and best man at a friend's wedding. They had not really spoken since high school, so he felt surprised to be kidnapped in this way and sad to miss out the gaming gettogether.
Next time the game community's members meet is in Stockholm. In October. Sandra and Jonatan are going to steal G. to be a witness at their burgess wedding. The idea is that this shall become a thing, making the friend to participate at a wedding each time.
A year passed since.
Jonatan and Sandra are now married.
G., as far as I know, was not there; nobody was invited, but the plan is to have a big party some time later.
Maybe G. was forced to eye witness some other wedding.