But Duchess Alexandra of Saxe-Altenburg, who married the Grand Duke Constantine Nicolayevich of Russia (second son of Czar Nicholas I) did actually become one: Prince Lennart Bernadotte of Sweden was born in 1909, the day before her 79th birthday. She died almost two years later, in 1911.
My question is: what are some other notable examples of royals who became living great-great-grandparents? This has undoubtedly been a highly unusual occurrence throughout history in general, not just royal. In the past, people married and had children young; but death rates were high in the days before modern medicine (although I realize that statistics are highly skewed because of high infant and childhood mortality rates).
But as medicine progressed and life expectancy increased, people have also put off marriage and children. As such, those whom one would expect to see great-great-grandchildren born within their lifetimes, by living to their 90's or beyond, oftentimes do not. Queen Elizabeth, the Queen Mother of Great Britain lived to the age of 101, but didn't see any descendants beyond great-grandchildren.
There could have been a five-generation portrait featuring the Swedish prince and his matrilineal ancestors, but for the fact that his maternal grandmother (born Princess Alexandra of Greece and Denmark, by marriage the Grand Duchess Paul of Russia) tragically died in childbirth in 1891.