The Question and Answer section for Titus Andronicus is a great resource to ask questions, find answers, and discuss the novel.
is that a serious question? merit is obviously the correct answer, or else main conflict in the play would not occur, namely the weaker but older son receiving the throne rather than the better brother.
In a lot of ways it ought to be a bit incomprehensible; it's a play about senseless violence...but understand what's going is generally a plus, unfortunately.
If you have time, try watching a production of the play on youtube or renting it...