The title says it all really, this is a gen/het story I read on FF.net, I think, as that's where I read a lot of gen. Don goes to see the widow of an agent and gradually gets involved with her and her two kids, who are very accepting. There's a blip when Don gets hurt on the job, but I think it ends with a wedding at the Eppes family house...

Title and author muchly appreciated, ta!