Is it possible to get messages from another phone without installing software on it?

Oh, this is something I worry about with my own grandkids too — they’re always on their phones and I can’t help but wonder what’s going on in there. Thank you both for the helpful advice; I didn’t know Apple had built-in Family Sharing options, so that sounds like a good place to start. Do those Family Sharing and Screen Time tools let you see who they’re texting, or just how much time they spend on the phone?