On this day in 1858, Theodore Roosevelt was born "in a brownstone house on Twentieth Street in New York City. A re-creation of the original dwelling, now operated by the National Park Service, replicates the tranquility of Roosevelt's earliest years. His father, Theodore Roosevelt Sr., was a prosperous glassware merchant, and was one of the wealthy old Knickerbocker class, whose Dutch ancestors had been living on Manhattan Island since the 1640s. His mother, Martha Bulloch, was reputedly one of the loveliest girls to have been born in antebellum Georgia. Together the parents instilled in their eldest son a strong sense of family loyalty and civic duty, values that Roosevelt would himself practice, and would preach from the bully pulpit all of his adult life."
On this day in 1880, Roosevelt, who had just graduated from Harvard, married Alice Lee. "On Valentine's Day, 1884, his mother died of typhoid fever and his wife died of Bright's disease, two days after giving birth to a daughter, Alice Lee."
In 1886, Theodore Roosevelt married Edith Kermit Carew. They had five children.
"No event had a more profound effect on Theodore Roosevelt's political career than the assassination of President William McKinley in September 1901. At the age of forty-two, Vice President Theodore Roosevelt took the oath of office, becoming the youngest President of the United States before or since. From the start, Roosevelt was committed to making the government work for the people, and in many respects, the people never needed government more. The post-Civil War industrial revolution had generated enormous wealth and power for the men who controlled the levers of business and capital."
"A conservative by nature, Roosevelt was progressive in the way he addressed the nation's problems and modern in his view of the presidency. If the people were to be served, according to him, then it was incumbent upon the President to orchestrate the initiatives that would be to their benefit and the nation's welfare. Not since Abraham Lincoln, and Andrew Jackson before him, had a President exercised his executive powers as an equal branch of government. If the Constitution did not specifically deny the President the exercise of power, Roosevelt felt at liberty to do so. 'Is there any law that will prevent me from declaring Pelican Island a Federal Bird Reservation? . . .Very well, then I so declare it!' By executive order in March 1903, he established the first of fifty-one national bird sanctuaries. These and the national parks and monuments he created are a part of his great legacy."
--from "Theodore Roosevelt: Icon of the American Century,"  Smithsonian National Portrait Gallery.
The Almanac of Theodore Roosevelt  is a treasure trove of information about the 26th President. Click the topics at the left and the links at the top to videos, store, family, etc.
The excellent Wikipedia article about Theodore Roosevelt  has an extensive bibliography.
In Theodore Roosevelt: A Biography,  Harcourt, 1931, Henry F. Pringle tells of the unsuccessful attempt made in 1910 by Cardinal Merry del Val, on behalf of Pope Pius X, to embarrass the former President. See pages 362-363.