2 Rembrandts have been hidden in a private collection for 200 years. Now they're headed to auction.

Two recently rediscovered Rembrandt paintings will be up for auction at Christie's in London next month, expected together to fetch between about $6.3 million and $10 million. They have not been seen in public since they were last auctioned off at Christie's – nearly 200 years ago. 

The two portraits depict relatives of Rembrandt, Jan Willemsz van der Pluym and Jaapgen Carels, who were an elderly couple, according to a news release from Christie's. 

The couple portrayed in the works came from a prominent family in Leiden, Netherlands. Their son, Dominicus van der Pluym, married Cornelia van Suytbroeck, the daughter of Rembrandt's uncle. Dominicus and Corneilia had a son, who is believed to have trained with Rembrandt as an artist.