I have a half brother
it means brother
I have a brother
The question 'Est-ce que Lucia a un frere' means Does Lucia have a brother? In the word-by-word translation, the verb 'est' means '[he/she/it] is'. The demonstrative pronoun 'ce' means 'this'. The conjunction 'que' means 'that'. The verb 'a' means '[he/she/it] has'. The indefinite article 'un' means 'a, an, one'. And the noun 'frere' means 'brother'.
I have fish in an aquarium
jean cavalier un frere
j'ai un lapin qui s'appelle hoppy means 'I have a rabbit called Hoppy'
I'm living in Paris and I have a brother
Perhaps you are a half-god.
J'ai un demi-frère. J'ai un frère consanguin. Demi-frère is much more common, but it ambiguous because it can mean either half brother or step brother. Frère consanguin is older/formal but only means half brother.
un et demi / une et demi
This is a poor and automated translation, meaning "I hope you have an amazing day with your baby brother"
un demi