Was Mercutio to blame for his death?

Was Mercutio to blame for his death?
At least in part. Tybalt was not looking for a fight with Mercutio. Mercutio actively picked a fight with him. It was his fault that he was in the fight in the first place. Maybe he might not have been stabbed had Romeo not intervened, but there is no guarantee of that. There is a guarantee that he would not have been stabbed had he never fought Tybalt in the first place.