In Search of a Sibling Name with the Right Ending
Many parents who are drawn to this style of name run into this problem. Today's fashionable surnames for boys almost all end in –n and –r. That gets repetitive as your family grows. And then you have the added complication of a surname starting with R.
To preserve the style of Easton but break out of the ends-with-N pattern, there are a couple of other groups of surname-style names with different ending sounds to consider.
The –ings: Channing, Fielding, Keating, Kipling, Manning, Sterling, Redding
The –s: Ames, Brooks, Davis, Hollis, Ellis, Miles, Reeves (and even some –ings, such as Hollings or Jennings)
The –tts: Barrett, Beckett, Bennett, Elliott, Everett, Prescott, Truett
The –ys: Bentley, Brady, Brody, Colby, Finley, Reilly
The single-syllable: Clark, Gray, Reid, Tate, Wade
Because of the sample names you listed in your question, I assumed you are looking for a boys' name. For girls, there are still many surname-style names that end in –n and –r (Addison, Emerson, Piper, Harper) that you will have crossed off your list. But you have more options that end in –y (such as Avery, Emory, Hadley, or Kinley).
Many of the names listed above for boys might appeal to you for a girl too—or inspire you to think of a variation or similar name that appeals. Here's to a happy ending for your family!