He is keeper of the family jewels — literally.

Now Greg Kwiat, the CEO of Fred Leighton Ltd. and CFO of Kwiat Enterprises, and his wife Alexandra, have just bought a new family home, in the form of a $5.295 million apartment at 19 E. 88th St.

The Kwiats liked the home so much, they bid over its $5.186 million asking price.

Kwiat, a 100-year-old family diamond company that did private label for giants like Harry Winston and transitioned into its own ultra-luxe brand about a decade ago, boasts celeb clients like Anne Hathaway, Natalie Portman and Jessica Alba. Kwiat’s new home, on a high floor, is a corner four-bedroom apartment with a library that comes with an en-suite bath that can be turned into a fifth bedroom.

The unit includes a roomy foyer, an eat-in chef’s kitchen and a planted roof deck that overlooks Central Park.