The definition of apropos, as defined by the Encarta Online Dictionary:

Apropos (adjective): just right

He came from a lower-class home.

She came from an upper class household.

He had a younger sister.

She had no one.

He was raised around constant strife and arguments that shook the walls of his bedroom.

She was raised in a household that often forgot she existed.

His parents divorced when he was seven.

Her parents died in a car accident when she was ten.

His father spent most of his time drunk and he had to duck out of the apartment more than once.

Her aunt, who was a huge figure in the fashion industry, made her into a model and robbed her of her freedom.

He joined a gang when he was in middle school.

She ran away from home when she was sixteen and worked on a pleasure cruise-liner.

He learned how to beat the snot out of people.

She learned how to manipulate the people around her to her best advantage.

He made friends.

She didn't.

He abandoned his gang.

She stayed on the ship, sharpening her dueling skills.

He was there when Seto Kaiba was soundly defeated by a kid half his size.

She had just won her fifth tournament when she heard about Seto Kaiba's defeat.

He snuck aboard Pegasus' boat so he could have a chance at winning the prize money for his sister's eye operation.

She just happened to be there when he was.

They both had vastly different backgrounds, with only a few common differences.

He may be the most street smart guy around, but any issue related to a woman and he turns into a dense log and loses all his confidence.

She may be the most sassy and savvy woman to walk the planet, but put her next to him and she turns into a pile of flustered insecurity (seriously, being that adorably thick should be outlawed).

His open honesty charmed her.

Her refusal to take crap from anyone earned his respect.

They both had communication issues when they had conversations. SERIOUS communication issues.

They both also had a singular ability to drive the other mad.

…

When one thinks about it, it's only natural that these two should somehow end up together.