User blog comment:B214/Shin DxD 1 discussion/@comment-181.115.108.207-20180827041432/@comment-31137559-20180827062750

Really it's just a title. If people are using people addressing him as prince then honestly it's just a title. Rias has been called princess multiple times. And I'm pretty sure Sairaorg has as well.

Basically all the children of the original Maou and their descendants would be princes and princesses in the Underworld.

It's just that some characters like Zekram and Apophis have addressed Rizevim as 'Prince Rizevim.' But that could just be something that those two address him as and there's no evidence they wouldn't address the other descendants the same. And it could just be those two being really respectful people.

Lucifer was called the 'father of devils' due to using Lilith's power to create the first generation of devils. I don't remember him being called the king of devils.

Unless you're talking about being a 'Maou' which is Japanese for 'devil king'.