What Constitutues a Biblical Marriage?

[Aquila]

In the United States we have a legal institution officially known as marriage. In various states we also have Civil Unions. In some states we have Common Law Marriage. In Ohio, and other states, those wishing to cohabitate without becoming entangled in the laws regarding what is officially known as "marriage" or "civil union" can file a "Cohabitation Agreement" that determines various responsibilities, roles, etc; nearly mirroring the stipulations of "marriage". These agreements also determine what is to happen should the cohabitating individuals terminate their relationship with regards to dividing property and assets. Alimony, child support, child custody, etc. might also be a part of the Cohabitation Agreement in some states. Most Cohabitation Agreements are settled in mediation without requiring court costs and the normal expense of a "divorce". Many local governments and corporations offer benefit packages for "Domestic Partners" who cohabitate just as they do "married couples".

Biblically speaking, do all of these classify as a form of "marriage"?

Should a straight couple who entered into a Civil Union be recognized as husband and wife?

Should couple who are legally married under Common Law be recognized as husband and wife?

Should a couple who have legally established a Cohabitation Agreement be recognized as husband and wife?

Thanks!