Nicola Peltz's Brother Will Peltz Engaged to Quincy Jones' Youngest Daughter

Nicola Peltz is gaining a sister-in-law -- who comes from Hollywood royalty. That's right ... her brother, Will Peltz, is engaged to Quincy Jones' youngest daughter, Kenya Kinski-Jones!

The happy couple announced the big news on Instagram Wednesday by sharing a black-and-white photo of them locking lips in front of the water -- with Kenya making sure her sparkler was front and center.

Nicola -- who, as you know, is married to Brooklyn Beckham -- erupted with joy in the comment section, writing ... "KENYA JONES PELTZ!!!!!!! MY FOREVER SISTER!!!! IM SO HAPPY I LOVE YOU BOTH!!!!!"

Paris Jackson even gave her approval, commenting a simple ... "yes !!!!!!!!!" Sylvester Stallone's daughter Sophia also chimed in with an enthusiastic ... "yay!! congratulations you two❤️."

Will and Kenya's engagement was a long time coming -- the pair has been linked for more than a decade and have never been shy about sharing their adoration for one another.

In May, Kenya celebrated the actor's birthday and sweetly told him ... "I love you from the very deepest place in my heart."

Kenya is shared by the late musician and actress Nastassja Kinski. Meanwhile, Will's parents are billionaire investor Nelson Peltz and former model Claudia Heffner Peltz.