Habe es selbst gelöst.
Hier das Ergebnis:

select
kennr||'/99' as kind,
null as vater,
name as bedeutung from Tabelle1

union select
kennr||'/00' as kind,
kennr||'/99' as vater,
vorname as bedeutung from Tabelle2

union select
Straße as kind,
kennr||'/00' as vater,
Straße as bedeutung from Tabelle3