“You see a doll, I see a baby that I never got to hold,” a woman says in a TikTok video while cradling a lifelike doll — known as a reborn doll — that has the chubby cheeks and sparse, blonde hair of a newborn. Another woman, Christina Keeler, who is married with two daughters, has a social media channel called “The Reborn Family,” with 38,000 subscribers. She gets thousands of views for videos in which she takes out the dolls in public outings. "I was never able to talk about our pregnancy loss until I found reborns," Keeler, who...