Two Russian mathematicians, Pavel and Grigori met at a conference in Vienna where the following conversation ensued:

Pavel: Grigori! It's been such a long time. How are you?

Grigori: Fine, Pavel. And you? I hope you are well.

Pavel: Indeed, I am. It must be fifteen years. You have children now, I believe.

Grigori: Yes two darling girls.

Pavel: And how old are they?

Grigori: Well, it's curious. The product of their ages this year is just three times the sum.

Pavel: I'm sorry, Grigori, but I still can't work out their ages.

Grigori: Of course. I forgot to tell you how excited little Nikki was when Pavla was born.

Pavel then knew the ages of the two girls. What are they? How old was Nikki when Pavla was born?