When writing a historical biography for an academic audience, there are usually a couple of thematic considerations that one wants to touch upon in one's analysis. These, of course, will vary from author to author, and what matters most is the particular argument you are trying to convey in your biography. Despite the fact that the very nature of a biography may make it seem as though a writer is limited to a strict set of empirical facts about another person’s life, the way in which one interprets these facts to create a compelling narrative makes all the difference.
For example, if you want to suggest that the circumstances of Button Gwinnett’s personal life influenced his decision to sign the Declaration of Independence, you are going to want to open your biographical sketch with a family history. Gwinnett, as you know, was born in England and moved to Savannah, Georgia, in his mid-twenties because of a number of failed business attempts in England and Jamaica. One might suggest, based on this background, that he felt somewhat disenfranchised by the English colonial system and that he therefore felt strongly about resisting the exploitative British business and colonial practices in America. This is a point made about Gwinnett in a very early biography of him, entitled Button Gwinnett, man of mystery : member of the Continental ... Clemens, William Montgomery, 1860-1931. I found this via the Library of Congress, and it is an open-access source. The link is here, if you are interested.
Using historical context to rationalize the decisions made by a biographical character is always the best way to explain the significance of their life. But this context need not always touch strictly upon the family background of the person in question. Sometimes it is more insightful to describe the political, economic, and social circumstances that influenced a person’s life choices in history. For example, there are thousands of biographies of Vladimir Lenin, and many of these examine his childhood—his birth to a middle-class, bourgeois family in Simbirsk, the political execution of his brother, and so on—as a source of information as to why he became such an ardent revolutionary. However, other biographers choose to take a different path. Historian Christopher Read, in his biography Lenin, discusses how his family upbringing combined with the tumultuous political circumstances with which Russia had been plagued and which young Lenin would have borne witness to firsthand. In this way, the circumstances outside of a historical person’s family also play an enormous role in determining their future attitudes and behavior.
Finally, some biographers choose to highlight a defining moment in a person’s life and argue that this moment served as a pivotal turning point in their life trajectory. Certain biographers of Hitler, for example, have made the argument that his rejection from art school, his imprisonment and subsequent publication of Mein Kampf, or the disastrous (from Germany’s perspective) Treaty of Versailles were major turning points in his life. You can see that these turning points were both internal, touching upon his life directly, and external, in that they greatly moved public opinion radically in favor of the ideology Hitler was espousing.
Whatever methodology you choose, what is important is that you use your evidence to make a compelling argument. Do not simply say, “In 1776 Button Gwinnett signed the Declaration of Independence…” Rather, craft your narrative in a way to explain the why and the significance: “The unique and circuitous circumstances of Button Gwinnett’s life meant that by 1776, there was only one rational option available to him—a declaration of independence from Great Britain. This is because…” Your evidence is not the end goal in itself; it is the means by which you make your argument.