How do you address wedding invitations to a family with a child over 18?

Once a child turns 18, they are legally an adult, so they should be addressed as such. If they live at home, you can still send one invitation to the parents, but write the adult child's name on the envelope. For example, Mr and Mrs Smith, and Mr James Smith. If the child has a title, such as Dr, use that. If they live away from home, send them their own invitation to their own address. This is the most respectful approach. It also means they can RSVP separately and decide whether to bring a guest. If you are inviting the whole family, but the child over 18 has a partner, include the partner's name as well. If you are not inviting the partner, do not mention them. The key is to treat the adult child as an individual guest, not as part of a group. This is especially important for seating and catering. If you are unsure whether they still live at home, ask the parents. It is better to send a separate invitation than to assume. Remember, an 18-year-old may have their own views on attending, so giving them their own invitation lets them decide freely.