Kids calling bf daddy

My kids dad and I are in the process of getting divorced. We have been separated for almost a year now. They are 3 and 1. Both my ex and I have started new relationships. Whenever we are around my current boyfriend my kids call him daddy. I cant blame them bc they don't know any better. We tried to correct them but it never worked. They know who their real dad is because he is still an active part in their lives.... does anyone else allow this?