Marriage Beliefs or Superstition (风俗还是迷信）

Most of my friends are getting married off one by one and I'm very very happy for them especially when it's two of my best friends that's about to be carried out their traditional wedding ceremony.  Anyway, one of them seemed to be facing a lot of problems with picking out the dates, as you know the Chinese has a lot of beliefs during the date for the ceremony and etc..... 

So, we were all discussing the problem on why she can't be marry before her fiance's sister get married first.  Since, our generations has been living in the modern society and didn't really follow the traditions and beliefs as much but the opinion of the elderly matters and quite bothersome at times.  Therefore, I've search through the internet and trying to find out as much information as possible regarding the matter and there's only one good explanations that I've found that make some sense but as a lot of chinese people does not follow the rules as they used to back in the days anymore. It's more of your own choice to believe it or not.

There's tons of superstitioin and traditional beliefs in Chinese Culture and society that if we decided to follow each and one of them, there will be no revolution of our culture.  Your life is put upon yourself to manage although at times there would be things that we can't control, such as fate and luck, but most of the time you can decide what you wanted to do and just do it if that makes you happy.

This is the result of our main discussion in mandarin but need to translate for my zCakes : 

1·同年有嫁有娶，要先嫁后娶。

(same year marriage in the family - female must marry first, then the male)

传统民间习俗认为：“先嫁后娶”即“先出后进”，寓意“添丁”吉利；不能先娶后嫁，“先娶后嫁””寓意“减丁”不吉利； 

(Tradition believes that if female marry first then male meaning adding "SON" therefore is a good sign but if male marry before the female = reducing "SON" = bad sign)

2·同年不嫁二女，同年不娶二媳。                        

(Two brothers or two sisters can't get marry in the same year)

传统民间习俗认为：“一年嫁二女”寓意“两嫁”不吉利；“一年娶二媳”寓意“再婚”不吉利。 

(Tradition believes that two sisters getting married = Double marriage = Bad Sign ; Two brothers getting married the same year = Re-Married = Bad Sign) 

参考资料：《增补万全玉匣记》东晋·许真人