In Paranormal Romance, we tend to have bands of brothers--men who are not actually related but unite and become family.
I have managed to find some great siblings in the genre though!
1. The Immortals After Dark by Kresley Cole
The Wroth Brothers
Warlord Wants Forever- Nikolai Wroth
No Rest for the Wicked- Sebastian Wroth
Dark Needs at Night's Edge- Conrad Wroth
Deep Kiss of Winter- Murdoch Wroth
2. Demonica by Larissa Ione
The Seminus Brothers
Pleasure Unbound- Eidolon
Desire Unchained- Shade
Passion Unleashed- Wraith
Ecstasy Unveiled- Lore
3. Celta by Robin D. Owens
The Holly Brothers
Heart Duel- Holm Holly
Heart Fate- Tinne Holly
4. Dragon Kin by G A Aiken
The Southland Dragon Brothers
Dragon Actually- Fearghus
About a Dragon- Briec the Mighty
What A Dragon Should Know- Gwenvael the Handsome
5. Dragon Lords by Michelle M Pillow
The Draig Brothers
Barbarian Prince- Ualan
The Perfect Prince- Olek
The Dark Prince- Yusef
The Warrior Prince- Zoran
6. Pride (The Shaw Brothers) by Shelly Laurenston
The Mane Event- Brendon Shaw
The Mane Attraction- Mitch Shaw
7. Klaus Brothers (The Klaus Brothers) by Penny Watson
Sweet Inspiration- Nicholas Klaus
Sweet Magik- Oskar Klaus
8. Psy-Changelings (The Kincaid Brothers) by Nalini Singh
Branded by Fire- Riley
Play of Passion- Drew
9. Argeneau Vampires (Argeneau Brothers) by Lyndsey Sands
Bite Me If You Can- Lucian
Born to Bite- Armand
The Accidental Vampire- Victor
10. De Piaget (De Piaget Brothers) by Lynn Kurland
If I Had You- Robin
When I Fall in Love- Nicholas
The Christmas Cat- Miles
One Enchanted Evening- Montgomery
Did I miss your favorite? Some of these series have more than one set of brothers running around. It was hard to choose.
To vote for for the best of the best, go to the Goodreads list: Best Paranormal Romance Series with Brothers.
Up next, Best Contemporary Romance Series with Brothers.