Co-Emperors and Symbasileuses 2: Born-in-the-Purple Also Available in Rome!

This is a recreation of my mod, "Co-Emperors and Symbasileuses" in CK2, ported into CK3.
(For anyone curious, here’s the link: https://steamcommunity.com/sharedfiles/filedetails/?id=1583784589 )

There has been a great update after the DLC "Roads to Power". Since the vanilla game now supports Co-Emperorship, the mod was updated to reflect the changes. The original main function of this mod was to allow emperors to have born-in-the-purple grandchildren by appointing their children as Co-Emperors. However, that was implemented in the vanilla game, hence reducing the utility of this mod slightly.

Nonetheless, the vanilla game still has problems. First, after restoring the Roman Empire, you would lose this mechanic if you moved your capital to Rome. This mod fixes that by allowing you to rebuild Domitian Palace in Rome after the restoration of the Roman Empire via a decision so that you can benefit from the Purple-born features even when your capital is Rome, not Constantinople (with the Bucoleon Palace). Of course, your culture should have the "Byzantine Traditions" Tradition.

This section is mostly for justification of this mod before the Roads to Power, but I thought there might be people who are still interested in it.

The "born in the purple" trait shows that the character was born in the Purple Chamber of Bucoleon Palace, Constantinople, when their parents were the ruling emperor and empress at the time of their birth. Historically, Porphyrogenitus or the people "born in the purple" had higher legitimacy than people who weren’t, granting a decent advantage to the descendants of the current emperor in the race to the Imperial Throne. Nonetheless in this game, when you get your grandchildren, they will not get this trait because their parents are not reigning at the time of their birth. However, this is NOT historical at all.

The Byzantine Emperors were not fools. Instead of threatening their own grandchildren’s legitimacy, they devised a clever bypass to this problem by making their heir apparent as "Emperors", often upon birth. The appointed junior, co-ruling emperors had full access to the "purple chamber", built with purple porphyry marble "all purple except for the colorful spots" and decorated with silk completely dyed in Tyrian purple, inside the imperial palace in Constantinople, thereby giving birth to fully legitimate "born-in-the-purple" grandchildren as the future heirs for the Empire.

The very idea of multiple co-ruling emperors dates back to Emperor Diocletian, who founded the tetrarchy where four emperors existed, two senior and two junior, each having an army and a set of provinces to defend. However as time flowed and the empire split in half, the title of junior co-emperor was not generally recognized as the sovereign of the empire anymore. Instead, the title of co-emperor acted as a de facto crown prince, just as the position that Prince of Wales holds in the Kingdom of England. Nevertheless, since they were "technically" (or de jure, so to speak,) emperors, their legitimate children were also considered to be Porphyrogenitus/Porphyrogenita, or born in the purple. There were several prominent cases where this fact affected the imperial politics in critical ways.

Any legitimate children (not Bastard, Wild Oat, or Child of Concubine) that were born between the emperor or the appointed co-emperor and his/her spouse AFTER the appointment (and the emperor’s coronation, if DLC and the corresponding game rule enabled) will get the trait Born in the Purple, given that they meet all the (slightly modified) vanilla requirements. Specifically, the emperor has his capital in either Byzantion or Rome with Domitian Palace, the emperor has either Byzantine Empire, Roman Hegemony, or Eastern/Western Roman Hegemony, and if the mother is not the emperor, then the mother should not be at war with the owners of the two counties (vanilla requirements for the mothers were "not at war with the father", but that created weird situations where the ruling Empress at war with her vassal duke husband failing to give birth to Purple-born kid.). Also, the culture of the Emperor should allow the "Born in the Purple" mechanics.

This feature is also maintained even after you restore the Roman Empire, provided you enact a decision (provided by this mod) to restore the Domitian Palace. Also enables Greek Fire decision after moving your capital to Rome (with Domitian Palace).

Does not change any vanilla files. Will be compatible with most of the mods.
Cannot guarantee compatibility with any major overhaul mods. Use them at your own risk.

"DLC Roads to Power" is required.

– Full support: English, Korean
– AI translation: Simplified Chinese, Japanese, Spanish (Spain), French, German, Polish, Russian

For the gorgeous Roman and Byzantine Coat of Arms, I strongly recommend Cat’s CoA mods:
https://steamcommunity.com/sharedfiles/filedetails/?id=2356992605
This mod was used in my playthrough and for the creation of the title image. I used it in the title image with his consent.