It's normal for a 7 year old boy to want to wear diapers and not be potty trained.
While some kids are ready to potty train before age 7, it's also common for boys to not want to be potty trained and want to wear diapers.
If your 7 year old son loves to wear diapers then you should, just let him wear diapers all the time until he decides to stop wearing them.
And even if he doesn't want to stop wearing them and use a toilet, you should just let him wear diapers for the rest of his life if he wants to.
Diapers are very comfortable to wear and I would've loved to stay in diapers when I was 7 years old.
Here's a few pictures of a 7 year old and 8 year old boy who also are still in diapers or at least were when these were taken.
The kid wearing diapers and in the box picture was taken in 2003 and the other pictures of a different boy named Tommy an 8 year old boy wearing diapers was taken sometime around 1996 or so.



