In Texas, I believe the typical sentence for vehicular manslaughter involving DWI is about 20 years.
From the Internet: Manslaughter is an unlawful killing that doesn't involve malice aforethought—intent to seriously harm or kill, or extreme, reckless disregard for life. The absence of malice aforethought means that manslaughter involves less moral blame than either first or second degree murder.
Twenty years sounds about right.