Sylvester insisted that his friends call him Syl. His parents, HOWEVER, continued to use his given name.
“However” is used to show contrast between two things. He is saying he wants to be called Syl, yet his parents still call him by his birth name.
Answer:
Sylvester insisted that his friends call him Syl. His parents. However, continued to use his given name.
Explanation:
If "however" is used to join two independent clauses you should put a comma after using the word. Putting it before is a gross mistake.
"However"" is used to introduce a statement that contrasts with or seems to contradict something that had been said previously.
I hope this answer helps you.
