My favorite quote from the movie:

Marty: Uncle Ethan

Ethan: Don't call me uncle. I'm not your uncle.

Marty: Yes sir.

Ethan: And don't call me sir, either. Or grandpa, or Methusalah. I could whip you to
frazzle.

That being said, I always wondered about the relationship between Ethan and Martha, his sister-in-law. The way they looked at each other and the way she caressed his coat when the Reverend snuck a look at her in her bedroom. I often thought that they were in love with each other but, for some reason, she married his brother. Maybe Aaron offered a more secure and stable life for her than Ethan. Maybe he was alot more wilder than she wanted but, she still loved him. And when Ethan rides to the burning ranch, the first one he calls for is Martha.