"I want to go home."
Translation:Dw i eisiau mynd adre.
Yes, "Eisiau" and "Angen" (To need) never need an "yn". This is due to them technically not being verbs, instead they are nouns that were used in a construction of "Dw i ag" (I am with- where no yn is needed due to there being a preposition). So originally it was "Dw i ag eisiau/angen" (I am with a want/need) which today has become "Dw i eisiau/angen".
Very clear and helpful explanation. Much appreciated, many thanks to Ellis
When I was a child at school, home was cartref. Where does adre come from?
I'm just a learner myself, but I think "cartref" is the place home (e.g. the house where you live) and "adre" is used for the adverb 'home' / 'homeward'.
I think "Dw i eisiau mynd cartref" would be something like "I like to go a house", which is a very obvious phrase. :-) I might be completely off track here though - but hopefully a native will see that and correct me! :-)