The first paragraph of the ‘The Family: A Proclamation to the World' starts by stating that the First Presidency and the Quorum of the Twelve Apostles. By saying this it becomes a declaration that this is scripture and a revelation for the Church of Jesus Christ. Additionally, it states that this document is official church doctrine.
These important men made this proclamation solemnly. According to the Webster’s dictionary the word solemn means 'formal' and 'dignified'. The order of the Family is not something that is to be discussed and debated with God. This word is at the beginning of the document to show that this is a matter by which the church and its members stand by and defend.
We continue reading in the Proclamation "...marriage between a man and a woman is ordained of God..." The Webster's dictionary shows us that one of the definitions of ordain is to order or decree something officially. God and his servants have helped us define the word Family by proclaiming that marriage is between a man and a woman.
As you can find in the Webster's dictionary another definition of ordained is to make someone a priest or minister. This definition can better describe a revelation the prophet Joseph Smith had on May 1831 that said "marriage is ordained of God unto man." This is a holy order that was conferred unto man. It is a calling of the priesthood.
In the first Paragraph of the Proclamation it states that the family is central to God's plan. It is the basic unit in the Celestial Glory. In a larger scale we are part of Heavenly Father's Great Family. But we can learn better in a much smaller scale. In a scale that consists of a man and a woman sealed by the power of the holy priesthood with their children, if any. In this much smaller scale we learn how to better depend on each other, support each other and care for each other.