Is my brother trying to smoke weed again?

I was on my brothers iphone checking my facebook and this random text comes up I accidently open it and its this huge conversation and the number isn't saved at the beginning my brother says do you have any herb? I don't know if hes just kidding or not because he jokes around like that but then at the end the guy says ill be in town for another hour, that's when I started believeing it was true my brother was smoking weed all throughout his childlife until he was like 20 hes 24 now