It happens, sometimes, that an Alpha will marry a Beta. That's what happened in his case, he married Helen, a Beta. But even though she's a Beta, it's plainly obvious she wishes she was an Alpha.

She's the one that brought Stephen to their home, without telling or asking. She drops him off and says nothing more than "Have fun, boys."

Nick recognizes him as one of his students which makes this even more complicated. He half can't believe she would do this but at the same time not very surprised. He swallows thickly, he can practically feel the heat coming off him from across the room. "She shouldn't have done this."