Children should not be having sex, sex is not for the young until they are married. Sex is only for the married. Ask her what she means by sex is for the children and young? Ask for more details in what is she saying what does she mean. I think it’s not the we are too old excuse but that she “doesn’t want” to have sex (doesn’t find pleasure in it) and that you do…is not making a difference I think she is being a bit self centered. I am a wife and I can understand where she is coming from, it’s not that I can’t enjoy sex it’s that I really don’t need it. I have four kids grown and now grandchildren, but because I recognize that he needs it, it’s my way to give back to him. Perhaps there is something about sex that she doesn’t like, perhaps it’s painful or messy or whatever, ask her these questions too, just ask her to be totally honest with you so you can understand where she’s coming from. There is a lot of great books out there, the 5 love languages is one of them, find her two strongest love languages, try to adapt your actions to her with them, it will help her to feel loved and perhaps she will return those feelings, it’s not a trick to get her to do what you want but instead it an understanding of what makes each person feel truely loved. (Including yourself)