Margaret - I do hope that your juxtaposition of gay marriage and embarrassing bodies does not mean what it suggests!
May I ask if you have done any research on the history of marriage in Britain?
I think you will find it had much more to do with male ownership of property , which included wives and children, and their wives' property, than it had to do with the safety of children.
Marriage, or bonding, customs vary widely over time and place. What is seen as normal in one culture would be seen as bizarre in another. There is nothing 'natural' about the legal contract of marriage. Many animals pair bond for life (although the female often makes sure she has a 'spare' sperm donor to help bring up the young). There are some 86 species of animals that have been shown to enjoy homosexual relationships, sometimes as a way of preventing aggression, sometimes as a form of birth control.
Who has the right to lay down for everybody else what is 'normal'?