Nicholas married Alexandra Fedorovna nee Princess Charlotte of Prussia, daughter of Frederick William III of Prussia. They had seven children in all. The eldest, Alexander, would eventually become Alexander II, Konstantin, would play an improtant part in the naval reforms of the 1850s and the Great Reforms a decade later. Of Nicholas's three daughters, the eldest, the blonde and blue eyed Maria, would become Duchess of Leuchtenberg, the black haired Olga, Queen of Wurttemberg but the youngest, Alexandra, who possessed considerable musical talent, would die only a year after marrying the Prince of Hesse-Cassel. Later, Nicholas and Alexandra Fedorovna had two more sons: Nikolai, who would later become the Russian commander-in-chief in the Russo-Turkish War of 1877-8, and Mikhail, later Inspector-General of the Russian artillery.
Nicholas I was regarded as the most handsome monarch in Europe. During his lifetime, many Russians admired him some even venerated him while others saw him as the personification of oppression. Anyone who lived during his reign could not remain indifferent to the force of his personality and the complex system which he imposed upon his country.
Suggest you read Nicholas I, Emperor & Autocrat of all the Russias by W. Bruce Lincoln.