Originally Posted by duke of poliganc
Her maternal grandmother Countess Ellinka von Einsiedel who is a descendant of the Prince Elector William II of Hesse and Prince Phillip is also a descendant of the house of hesse through his mother who was also a hesse princess but through a morganatic line .
Prince Philipp and Tatiana are related. Although the closest blood line comes from Philipp's father Prince Andrew of Greece and Denmark, and not from his mother Princess Alice von Battenberg.
Princess Tatiana's grandmother, Countess Ellinka Karin Harriet von Einsiedel (b. 1922) and Prince Philipp (b. 1921) are 5th cousins once removed, which makes Philipp and Princess Tatiana 5th cousins 3 times removed.
They are both descendants of Friedrich II, Landgraf von Hessen-Kassel (1720-1785) and Princess Mary of Great Britain (1723-1772), which is their closest mutual blood line.
Through this same line, Tatiana is 7th cousin once removed with her husband Prince Nikolaos of Greece and Denmark.