I love
Demetrius with the nickname Demetri, but I prefer
Nicholas with the nickname name
Nico/
Niko.
Baudouin seems rather awkward for a first name, but it might work as a middle name.
Demetrius Baudouin Ramses sounds cool or
Nicholas Roman Aleksei.
Other Suggestions:
Constantine Julius AlekseiAristarchus Roman Ramses (nick name
Ari)
Marcus Anselm BaudouinLeonidas Aleksei Roman