Family is important in many aspects of Batman's life, and more often than not, it goes the same for his villains.
One father figure that Batman has had to deal with is the father of Ra's Al Ghul, who goes by the name Sensei. A martial artist who can even trump Batman, Sensei is always a force to be reckoned with, even Ra's fears his own father when he arrives. At times, both Ra's and Batman have had to team up to defeat him.
Sensei often wants to be in control of the League of Assassins', but Ra's knows that his father is not as "pure" as him in his motives, and thus does all he can to prevent this from happening, including asking for help from Batman.