Thatcher wants to have his revenge on the royal family of Malynera because of what happened to his mother, who is Patalliro the 6th's aunt. 

Patarillo! is set in a society much like ours in most ways, with one decided twist. The manga on which it is based is one of the much-read works produced for adolescent Japanese girls that features a healthy proportion of gay men and beautiful teenagers aka bishounen (beautiful boys). Most of the action takes place in Marinera, the land of eternal spring, located somewhere in the South Seas. The country is a major producer of diamonds; they provide much of the basis of conflict in the anime series. They come from one of the most prolific mines in the world, owned by the king of Marinera, the vertically challenged but horizontally endowed boy-king Patarillo himself. The International Diamond Syndicate - a huge semi- criminal organization/ secret society dedicated to taking over the world`s entire diamond supply- wants that mine and will stop at nothing to get it. In the early episodes they send off a number of bishounen assassins to do in Patarillo, which necessitates his having a bodyguard, the English MI6 agent, Major Jack (`Bishounen-Killer`) Bancoran. Bancoran`s nickname doesn`t mean he shoots bishounen in cold blood. The soubriquet comes from the fact that no male under the age of 17 can resist his sexual fascination. This, to Bancoran`s eternal disgust, includes Patarillo himself. The action switches often from Marinera to MI6 headquarters in London (London seems to be an easy two hour`s flight from the South Seas) or Bancoran`s palatial condo in the suburbs of same. (MI6, be it noted, looks a lot like Fritz Lang`s Metropolis, while Jack`s `apartment` bears a passing resemblance to Randolph Hearst`s spread.) The action also goes into the past and future and out into space. Patarillo evidently gets around. 
(Source: aestheticism.com)

She is married to singer [Isao Sasaki](https://anilist.co/staff/96595) and is a childhood friend of fellow voice actor [Katsuji Mori](https://anilist.co/staff/95921).

Once, there was an island where it was always spring... 
...An island somewhere in the South Seas, with green forests and wide lakes. And mountains, let us not forget the mountains. Tall mountains with deep roots, filled with one of mankind's most precious treasures: diamonds. The name of this island is Malynera, and its king is only a child. 
Patalliro the 8th, King of Malynera, is ten-years-old. From the day he was born, everyone knew he was... unusual. He is a hyper boy, with flashes of genius, moments of thoughtless cruelty, and the ability to make a bad pun out of anything. Smart, but only a child and so he often does very stupid things. 
Patalliro! is his story. 
He lives in a world very similar to our own, but where the bizarre is commonplace. He manages to get into all kinds of trouble, from international terrorists, to space aliens, to accidental time-travel. His first challenge as king is to stay alive, when a group called the International Diamond Syndicate decides that they want control of the Malynera diamond mines. This is how he meets Bancoran, who was assigned to be his bodyguard during a trip to Britain. It's also how they meet Maraich, who was one of the assassins sent by the IDS. 
Patalliro is almost always accompanied by his army of Tamanegi ("Onions", so-called because of their onion-shapped wigs). The Tamanegi all wear identical masks, wigs, and glasses, and are known only by numbers. They are Patalliro's protectors, but protect the world from him just as much as they protect him from the world. 
(Source: cathion.net)