Wow, Shakespeare girl, that last post is really interesting. It took me back to my Roman Family Law course in college, where one of the basic rules we learned was that the Roman pater familias held the the "patria potestas" - the father's power. This power did in fact include the right of life and death. It also extended over the whole household, including all descendants in the male line (so the younger Lucius would be under Titus', not his own father's power, legally).
In practice, the right to kill one's own descendents was largely theoretical, and was eventually done away with, which was a very good thing, especially if you happened to be an ancient Roman. Of course, killing *other people's* descendants, which so far seems to be also much of what this play is about, was not okay (an exception in the play to this might possibly have been the death of Alarbus, since he's a captive of Titus, and slaves were under patria potestas. Except the whole human sacrifice thing was totally disgusting and seems highly, highly unrealistic for late Imperial Rome, but anyways...).
I wonder how much Roman law influenced Shakespeare in writing this play - I'll be watching out for these family law themes, as I finish up the play! (perhaps that will give me something else to think about other than "yuck!" and "gross!").