At least four Queens of the United Kingdom had adult children who pre-deceased them.
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