Answer
Maria Alexandrovna's first child was Alfred, who was born in 1844. He was the heir apparent to the Russian throne and was expected to succeed his father, Alexander II, as Tsar. However, Alfred died in 1865 at the age of 21, just a few years before Alexander II was assassinated. After Alfred's death, his younger brother, Nicholas, became heir apparent and eventually succeeded Alexander II as Tsar Nicholas II.