I don't have any sympathy for drunk drivers, but I don't see why a drunk driver who happens to kill two parents should be punished more harshly than a drunk driver who kills two elderly people, two college students, two parents whose children are all adults. All drunk driving is bad.
By this logic, why should a drunk driver who kills someone get a harsher sentence than a drunk driver who doesn’t kill anyone?
A drunk driver who killed someone and a drunk driver who didn't kill anyone have committed identical actions (drunk driving) but their actions have not produced identical results (one has killed someone and the other has not).
A drunk driver who killed an elderly couple and a drunk driver who has killed two parents of young children have committed identical actions (drunk driving) and those actions have produced identical results (two dead people).
Punishing the driver who killed the young parents more harshly than the driver who killed the old couple is assigning greater moral value to the young parents than the old couple.
And the law should not say that some people have a greater more value than others.
The two drunk murders
have produced different results. They have murdered different people, with different families. And even without this Texas law, they would be liable for the wrongful deaths of their victims, and their liabilities would depend on the details of the victims and their families. This law just formally establishes a predefined liability for a particular sort of drunk murder by car.