My 12 year old just got an iPhone. She has an old iPad that she has been using to text. She wants to be able to get texts on both the new iPhone as well as the iPad. Problem is, the iMessages she gets on the iPad are an aol account associated with an old apple ID. A couple years ago, we had to create a new Apple ID for each of our kids to be able to use family sharing. So she has 2 different Apple IDs. Is there a way for her to see texts for both on both devices?
Settings > Messages > Send & Receive...
You can add multiple email addresses there.
Also Settings > Messages > Text Message forwarding will allow you to send SMS to another device [I've not tested to an iPad but that's where I sent txts to my Mac]