On Days of our lives who is Phillip Kiriakis biological mother? Vivian or Kate?

I remember Victor sleeping with Vivian. Didn't she get pregnant by him? My mom says that she was a surrogate for Kate and Victor and Kate is his real mom. I remember a few years ago when Phillip had a gambling problem he was going to Vivian for money and calling her mom. Who is his REAL mom Vivian or Kate? Thanks.