Is this phrase correct?

Hello, I’m learning Latin on my own and I recently learned the second declension (masculine -us and neuter -um), and tried to create a phrase, this is what I wrote:

Romulus magnus, filius Rheae Silviae et dei Martis, est rex regni romae invictae et aeternae

What I’m trying to say is : Romulus the great, son of Rhea Silvia and the God Mars, is the king of the Invincible and Eternal Roman Kingdom. I don’t now if i wrote it correctly, please help me indicating the right path to the correct phrase.

The Latin has “king of the kingdom of invincible and eternal Rome.”

The good news is that what you intended to communicate was understandable from what you wrote. Bedwere already showed you what you actually wrote. In such contexts, Latin usually uses the adjective rōmānus, so “regnī Rōmānī” would be more idiomatic. That means you also would need to change the remaining adjectives to match.

Hello, thank you Mr. Bedwere for indicating me the translation of what I wrote.

Thank you Mr.Hofstetter, I also thought that writing “regni romani” would be redundant,
because I already said that Romulus was the king of Rome, so saying that Rome is a kingdom
would be redundant.

So in synthesis:

Romulus magnus, filius Rheae Silviae et dei Martis, est rex romanus. (Saying that he is a roman king)
Romulus magnus, filius Rheae Silviae et dei Martis, est rex romae invictae et aeternae. (Saying that he is the king of rome)

I two questions more:
a) Wouldn’t “rex romanus” mean he’s a Roman king, not necessarily meaning the king of Rome? (Like the etruscan kings of rome)
b) Why doesn’t the article “the” gets chopped out in the translation, it’s there a way of meaning “king of the invincible and eternal rome”?

Have both a good day.

Aelianus Adolphus

a) Since there is no article in Latin, it could mean either, depending on the context.
b) Again, there is no article in Latin.

You may want to revise your signature, since “virtum” is not Latin. I think you meant virtus, which is a 3rd declension, feminine noun.

Hello Mr. Bedwere, thanks for answering my questions, I forgot that
there is no article in Latin, as for my signature, I thought that
virtus was a masculine noun in the second declension (wrong because they end
in -o), so the following is a correction:

PERSEVERANTIA EST VIRTUS MAGNA

Following the rule that “A noun in the predicate referring to the same
person or thing as the subject is in the same case
”, which I didn’t follow
in the previous version of the signature.

Have a good day.