Please help be understand sentences below (Ars Amatoria 1,195-197)
Cum tibi sint fratres, fratres ulciscere laesos:
Cumque pater tibi sit, iura tuere patris.
1) What's the meaning of 'cum' here?
2) Who are they(fratres)?
3) What kind of rights do this mean(iura)?
Hostis ab invito regna parente rapit.
1) invito connected to parente? What's a role of 'ab here?
In “Cum tibi sint fratres, fratres ulciscere laesos:/ Cumque pater tibi sit, iura tuere patris “ (Ovid, Ars Amatoria 1,195-197) the conjunction “cum” means “since”, the plural “fratres” indicates the Roman citizens who are figuratively brothers of Octavianus Augustus, foster son of Caius Iulius Caesar, and finally the accusative neuter plural “iura” means “laws/rights”.
In short, “Cum tibi sint fratres, fratres ulciscere laesos:/ Cumque pater tibi sit, iura tuere patris” literally means:
”Since (cum) brothers (fratres) belong (sint) to you (tibi.Dative of possession depending on “sint”), avenge (ulciscere.2nd. person singular, imperative of ulciscor) [your] injured (laesos) brothers (fratres), and since (cumque) father (pater) belongs (sit) to you (tibi), defend (tuere, 2nd. person singular, imperative of tueor) father’s (patris) laws/rights (iura)” , i.e. :
“Since you have some brothers, avenge your’s brothers wounds, since you have a father, defend his rights”.
To conclude, Ovid encourages the young Octavianus Augustus to avenge the Roman soldiers killed in the battle of Carrhae and defend his father’s rights, i.e. Iulius Caesar’s rights, with reference to his foster father Caesar who endowed him with arms (see line 197).
As for “Hostis ab invito regna parente rapit” (Ovid, Ars Amatoria 1,198) literally meaning:” the enemy (hostis) stole (rapit,a Historical Present which in lively narrative is often used for the Historical Perfect) [his] kingship (regna) from (ab) the unwilling (invito) father (parente)”, the ablative “ invito” is connected to the ablative “parente”, while the preposition “ab “ (from) depends on the verb “rapit” ( literally, “steals from..”.).
Note that this enemy is Orodes II of Parthia, a son of Phraates III, whom he murdered in 57 BC, assisted by his brother Mithridates who was captured and executed in 54 BC by Orodes himself who was king of the Parthian Empire from 57 BC to 37 BC.
Therefore the enemy is Orodes II, the unwilling father is Phraates III.