When I was about 15 or 16, I told my dad, who smoked pot openly, that I smoke too. He didn't say I had to stop, but he didn't smoke with me until I was about 18 or 19. I respected that and I understood it. No hard feelings at all.

When I was about 25, I had a 15-year-old nephew, who thought I was a cool person, and I did smoke some weed with him, once. It cost me our relationship and the whole family was pissed at me because when some shit (long story) happened, the nephew mentioned smoking pot with me and the wrong family member heard it. The relationship with me and the family hasn't been the same since..so I would definitely let your cousin know that even though you smoke and you understand that he smokes, you don't wish to smoke with him until he is at least 18.