Eventually

Stephen Strange doesn't know Wanda Maximoff. Not really. But what he knows is that there is a mystical glow surrounding every fiber of her body and an immense amount of power running through the witch's veins.
He knows the Scarlet Witch is now a part of Wanda just like Wanda is a part of the Scarlet Witch and he swore to protect Kamar-Taj with his life, promised to keep any danger away.
And yet, Stephen finds himself mesmerized by the woman who's risking to break reality for her own selfish reasons.
With America Chavez by his side, he travels through the multiverse until he stumbles over the one that seems to overcome him by the core.

"You saw it too", Wanda's words are more a statement than a question and the look on Stephen's face is answer enough.
"Tell me Stephen". Her voice, an echo from another universe, another reality, another life he tries to ban out of his memory. "Why won't you let me travel through the multiverse to save my children. .. knowing they are your children too?"

AU where Wanda and Stephen stumble across a universe in which they are the parents of Tommy and Billy - A discovery that leads them to find answers for questions that have never been asked before.

Credits to the original author on ao3 :)