Hi RonneG
Do you mean he is leaking from the top, back,sides around legs of his diaper?
Could be many things
Things to check for
*Is the correct size diaper being worn
*Is the best fitted diaper for his body type used.
*Is the adequate absorbency of diaper being used.
*Consider higher capacity nighttime diapers like Northshore MegaMax, or Abena M4 or L4 style diaper. Others
* use of added booster pads, Tranquility or Northshore, others
* Frequency of changes needed per day.
Just thoughts and ideas to consider.