He had German citizenship though.In Germany the geography of were you born doesn't matter as much as where your parents are from.
If your parents are from Iran and stayed like 2 years in germany and give birth to a child then the child is NOT german. It is still iranian.
After a certain amount of time he can become german depending on certain criterias.
Also I am pretty sure Super Friendly Kitty Cat meant immigrant background. His parents weren't born in Germany so he in fact has an immigration background.