Happiness to all compatriots  Asgardians, I wonder if I can marry in Asgardian because I am madly in  love with a citizen and want to record our love in every universe.

How about something like a Civil Partnership which meets the following requirements:

* Age of Majority (for Civil Partnerships if that is different, not before 18 unless emancipated)
* consent from all parties involved (no duress)
* witnessed in person (or through live video chat)
* may file a Living Relationship Agreement (LRA) which is a non-binding document which is like a memorandum of understanding which would covers similar areas as does an Implied Monogamaous Relationship Agreement (IMRA). Many of those involed in non-monogamous relationships would have to negotiate these once going outside the boundaries of monogamy. This document would cover the following areas of agreement and negotiation where a typical monogamous relationship is merely a series of exclusivity clauses assumed for all parts:
  -- Social
  -- Intellectual
  -- Emotional
  -- Sexual
  -- Financial
  -- Parental
We could even have template examples or pieces parts for the LRA so it would be quite easy - drag and drop. It could even be done double-blind which would facilitate a conversation and the negotiation process.

Jealousy, Polygamy, and Polyamory

Let us now start a nation based on freedom and equality by oppressing sexual minorities. We can do better than that. I have written at researched and written at length about these and other social sexual issues on my blog (Gay Marriage, Polyamory, Polygamy, Prostitution, Understanding and Managing Jealousy; Implied Monogamous Relationship Agreement (IMRA); Polyamory, Jealousy, and the Eight Walls of Intimacy)

• Jealousy is a cultural thing and is taught. It is a strong byproduct of the effects of the the advent of Farming and the rise of Abrahamic faiths throughout the world. Believe it or not there are polyandrous peoples still existing and these societies tend to be egalitarian, peaceful, and matriarchal. 
• 
  
• Gender and Sexual Identity

Let us not be so reductive on gender and sexual identity. It is not so simple as the number 2.
I am very fortunate to be able to indentify as a cisgendered, heterosexual, heteroromantic male. 

http://keepmyncsafe.com/gender-spectrum/

*******

Agender
Androgyne
Androgynous
Bigender
Cis
Cisgender
Cis Female
Cis Male
Cis Man
Cis Woman
Cisgender Female
Cisgender Male
Cisgender Man
Cisgender Woman
Female to Male
FTM
Gender Fluid
Gender Nonconforming
Gender Questioning
Gender Variant
Genderqueer
Intersex
Male to Female
MTF
Neither
Neutrois
Non-binary
Other
Pangender
Trans
Trans*
Trans Female
Trans* Female
Trans Male
Trans* Male
Trans Man
Trans* Man
Trans Person
Trans* Person
Trans Woman
Trans* Woman
Transfeminine
Transgender
Transgender Female
Transgender Male
Transgender Man
Transgender Person
Transgender Woman
Transmasculine
Transsexual
Transsexual Female
Transsexual Male
Transsexual Man
Transsexual Person
Transsexual Woman
Two-Spirit

Marriage is born as a way to avoid the problems arising from the mortal struggle between our ancestors to obtain a mate to reproduce. Over time, we evolved, and this became a requirement of social acceptance, or social need in some cases. Nowadays, our view as a society has changed, and marriage is not imperative in the conservation of our species, nor truly necessary as the basis of our current society, even with respect to children. We are focusing on a new space society, with a different paradigm in the relationship between people, so the concepto of marriage should not be previously defined as inherited from Earth. So, I  think marriage and/or civil union as intended, should not be a concern for Asgardia.