Two very rich families are merging! One of the Hilton Hotels heiresses is getting engaged to the son of a famous European banking family. Nicky Hilton is engaged to James Rothschild, reveals Nicky's sister Paris Hilton via Instagram Wednesday, writing, "Congratulations @NickyHilton on your engagement! I'm so happy for you! You will be the most beautiful bride!"

"Such a lovely couple!" the singer/DJ added. "Love you both so much!"

The young pair began dating in 2011 after meeting at Petra Ecclestone and James Stunt's wedding in Italy. To add significance to the place, James decided to propose in the same country. "They went on a romantic anniversary trip over the weekend. He took her out on a boat into the middle of Lake Como and he proposed, got down on one knee and everything," a source said Tuesday. "It was incredibly romantic and beautiful."

The couple didn't wait for the wedding to go all out romantic! Nicky and James have been touring Lake Como, Milan and Rome since the engagement. "They are both really excited and happy," the source shared. "They are going on a road trip now throughout Europe celebrating."

Before the proposal. A source said that the European banking fortune heir secretly flew from his London home to Los Angeles recently to ask Hilton's parents for her hand in marriage. He seems to have planned everything to the tee!

Nicky has her plate full as it is though. In addition to wedding planning, Nicky has also been busy preparing for the Sept. 2 release of her book, 365 Style.