The Nina Williams vs. Anna Williams Sibling Rivalry
The story of Nina Williams and Anna Williams is a pretty complicated one. What was known according to Namco's official word is that Richard Williams their father favored Nina over Anna. Anna may have always sought her father's attention but was neglected. Nina learned assassination techniques, Anna did not thanks to the father's favoritism. Their father died and they both blame each other whose fault is it which can be seen. It seems to be most of Nina's endings are canon from Tekken 1-4. Note Anna DID NOT appear in Tekken 4.
Tekken 1 shows just a simple ending where both Anna and Nina fight in their apartment instead. Tekken 2 gets more serious when Nina's supposedly canon ending shows them visiting their father's grave. Nina just refused to make peace with her. Tekken 3 has a modification of Tekken 2's ending where she slaps Anna at the end of it.
In between Tekken 2 and 3, both sisters were placed in cryogenic sleep state for 15 years. Also in between that sleep state, Nina was artificially impregnated to give birth to Steve. Or perhaps she got pregnant before she gave birth to Steve which is boggling. Even the 15 years separation did not quench their rivalry as when Nina slowly recovers her memories after the cryogenic sleep, she is STILL hating Anna.
In Tekken 5, their rivalry resumes which can be seen in both of their Story Mode gameplay. In Tekken 6, Nina ends up working with Jin who is now ruler of the Mishima Zaibatsu. On the other hand, Anna works for Kazuya who controls G-Corporation. The sibling rivalry gets into a higher level when they are on the opposite sides of a father/son feud. What becomes of them will be discovered in Tekken 7.