Three of the last four queens were "Queen Consorts" (wife of a reigning king) who outlived their husbands; the fourth was a queen who reigned in her own right. Let's work backwards; the dates refer to birth and death.

1 Queen Elizabeth (1900-2002), widow of George VI and mother of the present Queen Elizabeth II, was predeceased by her younger daughter Margaret (1930-2002).

2 Queen Mary of Teck (1867-1953), widow of George V was predeceased by her second son George VI (1895-1952).

3 Queen Alexandra (1844-1925) widow of Edward VII and mother of George V, was predeceased by her eldest son Prince Albert Victor (1864-1892).

4 Queen Victoria (1819-1901), mother of Edward VII, was predeceased by three of her children: Alice (1843-1878), Alfred (1844-1900), Leopold 1853-1884).

An interesting pattern, don't you agree?

More Info: en.wikipedia.org