"My brothers sleep."
Translation:Fratres mei dormiunt.
Latin doesn't make a distinction between, "My brothers sleep," and, "My brothers are sleeping." You would say them both the same way, and whoever you're talking to would understand because of the context. Nobody would ever say that their brothers sleep, so you know when you hear it that the person who said it means that they are currently sleeping.
So as a general rule, if it sounds weird, it's probably the other meaning.
And it's like this in most languages. English has an unusual mandatory present continuous.
Pretty sure that's exactly why they chose this verb. Most verbs will sound fine in present simple or continuous. This one draws the attention to the fact it doesn't work like that in Latin (and other languages. Subject+ verb will usually do the trick for something that's going on right now, no form of "to be" necesarry or even possible. Some languages cán form a continuous, most will have a very different construction or just add "right now" if it's necessary, which it hardly ever is).
It has to do with the noun it's used with mei for masculine plural and meae for feminine plural.
Here is the full declension. (For now just worry about the nominative singular and plural If it's too much. Thats when something is the subject)
filius meus = my son
filii mei = my sons
filia mea = my daughter
filiae meae = my daughters
Remember Latin has grammatical gender, so this goes for objects too, not just humans. It's a masculine noun and not male.
As you can see the endings match, this is helpfull for remembering. This is not always the case though. Some nouns have an alternative ending (so not -us -a -um for masculine, feminine, neuter) like frater. It will still have the same forms of meus depending on the gender and number (and cases) though.
Frater meus = my brother
Fratres mei = my brothers
Mater mea = my mother
Matres maea = my mothers