So I gotta go off about Ravus for a hot sec here
This contains spoilers for Final Fantasy XV and Episode Ignis. This is your warning.
First off, we don't hear anything about the King of Tenebrae, which makes me believe that he died when Ravus and Luna were just children. So Ravus is already the man of the house. Then Niflheim invades and murders his mother in front of him when he was only 16. He lost both his parents at this point, so all he has left are Luna, Umbra and Pryna, though the latter two are Luna's dogs.
So he and Luna spend a few years as prisoners, and he joins with Niflheim due to his belief that Regis could have saved his mother but he did nothing. So when given the opportunity, he participates in the attack of Insomnia, and takes the ring of the Lucii. Well, that doesn't end well and bye-bye arm. This is his second traumatic event with fire (tiny headcanon that he is afraid of fire)
(Sidenote, can we just talk about that physical change that followed that event?)
He is given a prosthetic arm that was made the same way that the Nifs make Magiteks, so it is laced with the starscourge, just enough to most likely explain his sudden changes in appearance, like his hair going silver and the eye color change from grey to blue and purple.
Now it's off to Altissia, where Luna, who is getting really sickly, is to summon Leviathan. She and Noctis get separated from the others, and Ignis sides with Ravus as they go to find the lovers. But they were too late: Luna has died. Ravus lashes out and, if I remember right, he says something about losing everything. And that he has: he has no family left. It's just him.
After the battle with Leviathan, Ravus is blamed for a lot of the destruction, and is set to be executed, as noted by a newspaper you can read while on the train to Niflheim.
And as seen in the Chapter 13 little bonus scene where you play as Gladio and Ignis, he is attacked by daemons before falling from a pretty good height, and he attempts to return the blade of the father (I cant remember its exact name) to who he believes is Noctis, but it turns out to be Ardyn. For a brief bit after that, the player is made to believe that he died there, having got his prosthetic arm cut off, which was the source of his strength.
But no. Ardyn is too big of a dick to let the last Nox Fleuret die in piece like that. You make it to a hanger area, and suddenly, he's there. Half daemon and begging for you to kill him. Pleading you to end his suffering.
You do, and from what I have heard he is a tough boss (idk I was crying 90% of the battle) He finally gets to rest and be with his family once more.
TLDR; Ravus has a shitty life and he needs more love
