In the season 12 episode "I Choose You", Alex's later-second wife (Camilla Luddington) finds an invoice from the fertility clinic that housed Izzie and Alex's fertilized embryos from when she had cancer and ponders the possibility that he has children with Izzie.
The discovery of an invoice related to embryos created during Izzie's cancer treatment in season 12 episode "I Choose You" prompts Camilla Luddington, Alex's second wife, to consider whether or not he has children with Izzie.