His Surrogate Omega by Kelex

Omega Gray Tomlinson is positive he’ll remain unmated for the rest of his life. By his mid-thirties, he remains unclaimed and without prospects, and lives confined to the Omega Quadrant, where he’s sure he’ll end up dying alone.
When his older brother, Silver, and Silver’s alpha die in a tragic accident, Gray’s nephews come to live in his little sequestered world. Without an alpha, he knows he has little means to help support the boys. The only choice he can stomach is to offer his services as a surrogate.
The minute Gray meets Jamie, the infertile omega who so desperately wants a child, he senses a bond like none he’s ever felt before. It’s brotherly love at first sight, and Gray decides Jamie is the one, agreeing to carry his and his alpha, Rohan’s, child.
But when circumstances change, Gray is faced with new challenges, a new love interest, and a battle for the very life that grew inside him. And maybe there’s an alpha out there for him after all…