And Then There Was You by Kathryn Basham

Jack Robb has always been protective of the people he loves, even at the expense of his own needs. Especially the friends that became the family he never had.

Until one horrible night changes everything.
Now, he finds himself stepping up for a friend facing an unimaginable loss. And as much as he wishes he could shove his own grief down and ignore it, helping her means he has to face it. But he can’t walk away.
Not from her, or from the unexpected little one who already feels like his to protect.
So he stays.
Through the quiet nights. The overwhelming days. The moments when her strength falters and she needs someone to hold her together.
But somewhere along the way, the lines blur.
Because the way she looks at him starts to mean something more.
Because being there for her starts to feel like everything. Because protecting her starts to feel a lot like loving her.
And that means confronting the one question he doesn’t want to answer.
How is he supposed to fall for her when it feels like betraying the person who meant the most to both of them?