She was originally just the second wife. Princess Emma of Waldek and Pyrmont married the elderly King Willem III of the Netherlands two years after the death of his first wife, Queen Sophie. He was forty-one years older than her, and had two adult sons, both older than her.
Six months after the wedding, in June 1879, Crown Prince Willem died in France from typhus, and his younger brother Alexander became heir.
Meanwhile young Queen Emma gave birth to her only child in August 1880, a girl called Wilhelmina.
Meanwhile, tragedy struck again; Crown Prince Alexander died in 1884. The king became ill with shock, and Queen Emma took over his duties as Queen Regnant. The King died in 1890, leaving the throne to his ten year old daughter, Wilhelmina.
Then began a remarkable matriarchy. Because Wilhelmina was under age, Emma was Queen Regent till her daughter turned 18.
Thereafter she devoted herself to supporting her daughter and grand-daughter (Wilhelmina had just one child, Juliana).
These ladies saw the Netherlands through both world wars. Despite the occupation, the Netherlands came through with dignity, because unlike in France, Queen Wilhelmina refused to sign the surrender papers and instead appointed a government in exile.
Queen Emma died in 1934, so didn't live to see her great-grand-daughter Beatrix being born. Beatrix would be the third Dutch Queen in a row.
Here's a picture of Queen Emma.
She looks remarkably like her great-great-grand-daughter Crown Princess Catherine-Amalia who will be the next Dutch queen, continuing the matriarchy Emma started.