Luffy is Very Sincere Character

 There was a period of avoidance after the Sabaody Arc when the team self-destructed and prepared for quite a long time independently. The entire team, including Luffy, became more grounded and developed throughout this time. 

• Jinbe: He joined the team after Luffy requested that he join after the time-skip. Jinbe is a previous Warlord. He always very found of his friend and asked how old is luffy?

 Luffy is as yet matured 19 in the Wano Country Arc. The author of One Piece, Eiichiro Oda, talked about the age issue in a new volume. He clarified that even though the story is long, the occasions are constant. And full story is displayed on theinfotrunk.