I’m a reader in Kansas with two teenage daughters, 16 and 18. My girls recently met a boy where they work and both took an interest in him. The 18-year-old was devastated that he was more interested in her younger sister. I spoke to the 16-year-old about it, which is when I found out this boy is going to be a sophomore in college. The fact that he’s interested in a 16-year-old is a red flag. I asked the 16-year-old to keep her distance. She agreed, but I saw a shirtless photo he sent her. I don’t know what other photos he’s sent and I don’t know what she’s sent him, but I immediately removed all photo apps from her phone. The girls have had public fights about this boy. They’ve made peace with each other, but now my 18-year-old wants to date him. I can’t control the actions of an...