The Reluctant King by M. Merin

Vadim
Raised as an errand boy for the Bratva in St. Petersburg, I learned young to keep my mouth shut and my ears and eyes open. The Kuznetsov family became the only family I ever knew.
When I was brought to the Boss’ attention, I knew it was because of my loyalty and brutality. Artem needed a man with no further hope of advancement, who would willingly serve as a role model and advisor for his only legitimate son, Josef.

Natalia:
My earliest memories were of being tormented by my brother.
My earliest lessons encompassed what my husband would someday expect of me.
Raised in a palace, I watched each of my sisters forced to marry at my father’s whim. I became his favorite, hoping one day he would be merciful when choosing my husband.
I admit I am spoiled and when I knew what I wanted, I defied everyone – even Vadim – to get my way.
Now, we just need to find a way through this without being killed.