G.C.
Hi K.
Barring any physical problems, babies need to go back to sleep independently. All kids wake up in the night, most go back to sleep without waking parents.
I am a firm believer that kids understand a lot more than we think so I talked to them honestly about everything. Tell her that she needs to learn to go back to sleep on her own like most big kids do. Tell her she is not to cry in the middle of the night, but must close her eyes and breath slowly and try to go back to sleep. I lay down with my daughter in the afternoon and we practiced closing eyes and breathing slowly to go back to sleep, then I told her she was old enough to do this on her own. I told her I would not come to her in the night if she cried except to remind her to close her eyes and breath slowly. After a few nights I told her I would not come to her in the night to help remind her anymore because she was clever enough to remember on her own.
It worked for me. Babies respond the the stimulus in their environment. By coming in a loving them back to sleep we reinforce the waking. Cuddle them in the morning instead and let them know how proud you are that they are able to go back to sleep on their own.
Good luck with the 13 yr old. I found that age less easy to read!!