There are several conflicting legal theories in this case.  The first is jurisdiction (which court has the authority to hear the case) and that will generally be settled by the two trial judges hearing the case but must comply with the Uniform Child Custody Jurisdiction Act.  Alaska had it to start with but may now have to share it with Texas.  Then there is ICWA which as to custody of Native children, pre-empts State law.  Native relatives have the preference.  Finally, there is the presumption against granting a domestic violence perpetrator custody.  I doubt that dad will ever have custody or visitation with these kids but that is not guaranteed.  If they are settled in Texas, let them stay there - it's their best interests which should be the deciding factor and not legal gamesmanship.