In the beginning of Maleficent, King Henry led an attack against the Moors, but Maleficent injured him. On his deathbed, he promised the throne to whoever would kill Maleficent, which led to Stefan cutting her wings off and presenting them to the King, thus he becomes Princess Leila’s husband and the new King.
But where was the Queen (King Henry’s wife) during this?
Did King Henry kill her to have all the power? Was she a fairy queen?
We don't know. King Henry and his daughter Leila are minor characters and their backstories aren't well developed. It's not known how he gained the throne or who his parents were, nor who his wife was or her fate. Certainly he places a lot of stock in 'royal blood', so at the very least we know that he's an aristocrat and his wife likely was one as well, and given his hatred for all things magical, it's very unlikely that she wasn't human.
Stefan beamed. He’d finally done it. He’d overcome his status as a poor orphan to become something great. “I shall do my best to be a worthy successor, Your Majesty.”
“Successor? You?” Henry gaped at him in surprise.
“As by your edict.”
The king allowed himself a throaty laugh. “You? Your blood is not worthy. You are a servant, nothing more. I don’t even know your name!”
His daughter (the Princess Leila) is in her 30's, so her mother would be likely to be in her mid-to-late 40s or early 50's by the time the film takes place, which was relatively close to the normal life-expectancy for an aristocratic woman in medieval times.
In short, given her total absence from the film, she's probably dead.
