The Tennis Players

Zita, her brother, her daughter, and her son are tennis players. As a game of doubles is about to begin:
[1] Zita's brother is directly across the net from her daughter.
[2] Her son is diagonally across the net from the worst player's sibling.
[3] The best player and the worst player are on the same side of the net.
Another Simple question-Who is The Best Player?
{Level-Medium}