Thanks Brigid/Malika.
Yes I also think it is not that simple.
It probably depends on the exact wording of the implementation of the European directive into Irish law.
If it says the sponsor must be an EU citizen which is not a national of Ireland; then it can be argued that as long as you are Irish you are excluded (in that case it would specifically say you cannot be Irish).
If it says the sponsor must be a national of an other EU country than Ireland, then as long as you are German you should be included (in that case it wouldn't specifically say that you cannot be Irish).
The other potential issue I can see is that the directive says that the EU citizen must have exercised their free movement right to enter their host country.
I guess if you are both German and Irish, it could be argued that in order to enter Ireland you don't need to exercice your EU free movement right because as you are Irish you are free to enter anyway.
In my case though, the German citizen first entered Ireland as a German national only, and has now became an Irish national through naturalisation. So I guess he did exercise his free movement right ... but as it probably is a pretty specific case; it is difficult to know whereas the immigration officers would take that into account when reviewing the application (plus they could say that the first time you leave Ireland for holidays as an Irish and come back then you are not under the EU free movement case anymore).
I will hope Monife has a look at this topic then