Intro: Outline debate, define key concepts (eg. Nuclear Family, try and keep it reasonably short)
Paragraphs 1 and 2. ''One reason sociologists may think the Nuclear family is functional....''
''A further reason sociologists may think the Nuclear family is functional....''
Paragraphs 3 and 4: like last ones but opposite.
Conclusion: 'Having looked at both arguments, the weight of evidence suggests..'' (come to a clear conclusion. Also don't put absolutes (such as never, ever, always), they are rarely correct. Especially in a sociology essay.