I can't remember the title or actors, but a girl goes for a high power job. She sees the super rich boss who assumes she's there fir the post of his children's nanny so she ends up as nanny to his two children. A boy & a girl.
It's a sort of modern day fairytale come rom com, with a wicked plotting fiancé who tries to steal our heroines business ideas, but comes a cropper as the children and nanny eventually team up to expose her for who she really is.

I think it’s called The Nanny Diaries

Sadly it's not the nanny diaries. The guy is unmarried but has a conniving fiancée who attempts to pass our heroines work off as her own.
He may be royalty or something as he owns a big Bavarian castle.

Au Pair

Au Pair