As most of species, humans have always thought that the most simplistic and natural of taking a lifespan relation is bigamia, but this mostly relays in the place where it happen, as sometimes culture does not allow bigamia, even if the laws do.
As most of species, humans have always had the thought that monogamia is the most natural and simplistic way of having a lifespan relationship with someone. Some humans, as some places allow it, can have poligamia (more than two people in the same relationship). Even though this is very uncommon among normal humans, the ones that stand in the top end of the power stair might be seen with more than one partner. Most of the cases of poligamia in the Colossuss Galaxy have one female and more than one male in the relation.
The act will be executed by the partners and a designed person by the city hall. The wedding itself most of the time is not celebrated in the moment, but days or hours later. Not as in earth, weddings are something that top class humans take very seriously, as sometimes it also brings benefits with it and it is something that once broken, can't be repaired. If one person of the couple decides to "divorce", a legal war would begin in order to keep the most things as possible from the other member. Also, they both would be sometimes excluded from society in some ways.
Components and tools
Most of the time, humans try to wear blue clothes, as blue means prosperity/ union in some places. Other times, people would wear red and simplistic clothes as a symbol of good luck, remembering the flower of Tripia.
Always, the closest friends of both partners are invited, but the group is never bigger than 20 people, as the celebration will take place in other place.