Depending on the age of your child and grandchild maybe you could explain how to be a good role model. You could allow the baby talk but also explain that your child needs to talk like a (however old your child is) because as the grandchild grows up the grandchild will watch your daughter and try to explain as a good role model it is your daughters responsibility to show your grandchild how to act at different ages. I am not sure if this is age appropriate but I use this a lot with my daughter who is obsessed with younger children and is more comfortable with them then her peers. This helps prevent meltdowns because I am not telling her what to do, but making a suggestion and this way she still feels very important. Thank you for sharing and good luck.

My 17 year old is approx the emotional level of a 5 or 6 year old. I don't want him playing with baby toys so we have worked on teaching him to like stuff more around the 10-12 age group. When he tries to get a "baby" toy or book, I just say, Oh those are for babies... you're a big boy. Look here's some big boy books. So far, that is working.... but I think the part that makes the difference is offering the alternative. You can't just "that's not right" without offering what is "right".

I'm in the same boat. My step son is 8 with ASD and his brother, my natural son is 1. Tough situation. I know his mom gets irritated with the regress, but thank you for posting this, I'll be sure to follow this Q&A!

Always offering choices no matter in what situation