Unmei no Ω: Soredemo Boku wa β no Kimi wo Aisu

Even betas and omegas can have children. With the goal of making a happy family, Tatsuki (omega) and Ryodai (beta) have been living together for three years. Just when they were at the height of their happiness and thinking about marriage, Okishima (alpha) finds Tatsuki. Feeling something different than with other alphas, Tatsuki immediately goes into heat!! With the appearance of his "destined partner," Okishima, Tatsuki and Ryodai's relationship starts to collapse. As much as he would rather be with the one he loves than the one fate has chosen for him, his body just won't listen... A heart-wrenching Omegaverse love story torn apart by fate.

(Source: Shusuisha)