So, how old is Chewie when he witnesses his best-friend being murdered at the hand of his own son?
We know that Han Solo is about 15-years older than Luke and Leia. There is a 19-year gap between the events of Revenge of the Sith (the birth of Luke and Leia) and A New Hope (when the gang gets together to blow up the first Death Star). The events of The Force Awakens (Episode VII) and The Last Jedi (Episode VIII) takes place 34-years after the events of a A New Hope.So let's presume that the events of Solo take place 14 years before the Battle of Yavin.
190 (Chewie's age in Solo)
14 (time between the events of Solo and a New Hope)
+34 (time between a new Hope and the New Trilogy)