Ok, so this is my first theory blog on this wiki.
I have been thinking for a while now about who Luffy's mother might be, what if she was a princess or a queen?
Monkey D. Dragon could have met her in some country and fell in love with each other. But due to their status, they have to be secret from each other. She ended up pregnant with Luffy and had to ensure his safety (like Portgas D. Rouge).
That would explain Luffy's significant interactions with princess characters or females with royal authority or family status.
What are your thoughts?