Whose children are Lucie and Lea?

From the first meeting of Ahmad with the two children, Fouad and Lea, it is not at all clear whose children they are. It is soon revealed that Fouad is Samir's son. Later, Lucie talks about going to live with her father in Brussels. That leaves little Lea. I suspect that she might not be Ahmad's daughter, as she calls him "Ahmad." It would be very helpful to have a summary of Marie-Anne's past relationships, besides Ahmad, but I am still not at all sure. Is this rather vague situation intentional, perhaps to show that the past is not crystal clear?