Mr. Tan was Dana's father.
Mr. Tan was very protective of his daughter, and did not like her boyfriend, Terry McGinnis, who had a troubled past. Though Dana had tried to convince him her boyfriend had changed, Mr. Tan still thought she deserved better. When Dana failed to return from a date one night, Mr. Tan stormed Terry's house looking for answers, but he didn't have any. He threatened Terry if his daughter wasn't found, although she was ultimately found, much to her father's delight.
In Paul Dini's screenplay for Batman Beyond: Return of the Joker, there was a line in which Mr. Tan was indirectly mentioned that didn't make out in the finished version of the film. In the scene where Terry is explaining to Bruce why he wants to go on being Batman, Terry says that the disapproval of Dana's father is a constant reminder that he'll never completely erase his criminal past.