Actually, that is not true. Although the term father would represent a male that gave DNA for a child to be born, the term is meant to represent the one who gave half of their DNA for the child. Dani is created from all of Danny's DNA with only small mutations (which would be the reason she is a girl and younger than him).
As such, if someone were to look at their DNA samples without having any knowledge of the situation, they would only believe them to be siblings because the DNA would have too much in common. Jack would be the one that came up as the father because approximately half of his genes would be inside Danielle, just as approximately half of Maddie's genes would be in her.
Oh my... Never actually thought about it. ;T Well biologically it probably does. But in my logic - no. But your point of view is quite interesting actually. If Danny is her father, then... Oh my... Vlad is a mommy? xD