What kind of person in your opinion would each brother fall for?
Hmm, I think canonically the brothers each have a very wide spectrum as it's really the uniqueness of MC that they're drawn to. So in all honesty, they'd be drawn to MC no matter the personality.
But! If we go by my headcanons...
[Disclaimer: all headcanons are valid!]
The presumption: someone submissive
The reality: someone he can kneel to
Yes, yes, we've all been told he's a sadist and he certainly gave of those early dom vibes, but as Lucifer has opened up, we've seen he has a very soft and squishy centre. We also know he loves to obey - if the master is worthy.
Lucifer is drawn to those with razor wits and easy smarts, who can challenge him to chess or verbal sparring and leave him with his heart racing regardless of whether he wins or loses.
Confidence and bravery are his undoing, and being vulnerable in his eyes is what he considers the bravest of all.
The presumption: someone dominant
The reality: someone who praises and protects him
Mammon craves being told what to do, but not at all for the right reasons. He falls into that role for safety, reasoning that if he is not responsible for his actions, he can't be mocked or blamed or hit.
A person who instead lavishes him with praise will reduce him to a puddle of blushes, and a person who stands up for him against his brothers absolutely floors him.
Whatever the person is interested in or passionate about, Mammon is happy to learn and share his own loves. He is devoted to the person who loves him for who he is, not who he forces himself to be.
The reality: someone who shares their passions
Sure, shared hobbies are a great help, but what really appeals to Levi is someone who not only shows interest in his passions, but who shares their own passions with him.
Everyone is a geek for something, and he loves exploring new interests with a person that gets so excited about them.
More than anything else, Levi values time spent together. It's very hard for him to doubt how much a person enjoys his company, if they spend so much time relaxing and laughing with him by their side.
The presumption: a submissive bookworm
The reality: a bold adventurer
Like his father, he is a presumed dom and even sadist, with more than a passing interest in petplay. But what really excites Satan is exploring new places, experiencing new things, trying everything the world has to offer.
Someone who will not only join him in that but take the lead, organising new things for him to see and do, is a breath of fresh air in a world filled with rules and regulations.
He is as happy to be bossed about as he is to take the reins, but the kitty ears are definitely a plus.
The presumption: a sexoholic
The reality: someone who loves him, sex optional
The Avatar of Lust would seem to have one very obvious key to his heart, but it's a misdirection that very few ever pick up on. Asmo believes only his beauty is of value, not his actual inner self, and someone who can see through the surface and still want to be with him will forever have his heart.
In many ways, he is the most vulnerable demon, his armour of lust monster incredibly thick. Unlocking the trembling angel within takes perseverance, and setbacks will have to be overcome.
All of his innuendo is a mask for what he truly craves - love and affection. Soft cuddles, kissing for hours, holding hands... these are the things that really make his heart skip a beat.
The reality: someone who listens to him
Beel is hungry, this we know, but he is also less hungry when with the person he loves. His mind becomes clearer, and he's able to share all the thoughts and feelings he normally keeps inside, not wanting to burden anyone with his words.
With the person who he first confessed his feelings of crushing guilt to, he finally feels like there is someone who truly hears him when he speaks, a small mouse to his giant lion, that he will protect with his very life.
That this person isn't scared of him, instead seeing his gentle nature with his pain buried deep, allows him to ask for what he most wants - cuddles, pets, and reassurance of his worth.
The presumption: fuck knows đ
The reality: someone who surprises him
It's very hard to tell what vibes Belphegor might be putting out, as he does his best not to put out any. His rage is legendary, as is his ability to sleep through anything, but he is also effortlessly clever, dryly humorous, and with surprising talents like dancing and perseverance.
Above all however, Belphie is a brat. He loves being told what to do, almost as much as he loves deliberately disobeying. The person who can outfox him and keep him on his toes will steal all his attention. Unpredictability is incredibly attractive to him, as is anyone who can out-brat his wicked ways.
(All the above is canon to my Obey Me fic đ)