How were Wilhelm II and Elizabeth II related?

Elizabeth II was the first cousin twice removed of Wilhelm II.

Their nearest shared ancestors were Victoria and Prince Albert of Saxe-Coburg and Gotha.

That is only the shortest of 5 separate lines of descent between them.

The line between them

1. Wilhelm II 1859–1941
2. Victoria, Princess Royal 1840–1901
3. Victoria 1819–1901
4. Edward VII 1841–1910
5. George V 1865–1936
6. George VI 1895–1952
7. Elizabeth II 1926–2022

See the line on the tree