Head canon 3#: Mother Gothel never told Rapunzel how babies were made or she did tell her but then told her that no man would ever want to have children with her.

"How are babies made?" Rapunzel asked Eugene.

"Well that's usually something people ask their parents," Eugene said. "Err, did Mother Gothel ever tell you anything about it?"

Rapunzel shook her head. "She said that no one would ever want to have children with me anyway."

"That's not true. I'm sure you'll make a great mother one day." Then he gave her a hug. "But seriously ask your parents," he added.