Mary-Kate or Ashley? Elizabeth Olsen Reveals Her Favorite Sister

She had a good reason for her choice.

ByABC News
February 20, 2014, 5:50 PM
Mary-Kate Olsen, Ashley Olsen and Elizabeth Olsen attend the NYLON & AX Armani Exchange Private Dinner for the October issue with cover star Lizzie Olsen, Oct. 5, 2011 in New York City.
Mary-Kate Olsen, Ashley Olsen and Elizabeth Olsen attend the NYLON & AX Armani Exchange Private Dinner for the October issue with cover star Lizzie Olsen, Oct. 5, 2011 in New York City.
Jamie McCarthy/Getty Images

Feb. 21, 2014 — -- If you are an Olsen fan, it's the question you've always wanted answered: Which Olsen twin, Mary-Kate or Ashley?

When little sister Elizabeth Olsen, 25, was put on the spot on "Watch What Happens Live," she made her choice of favorite twin -- the twins are 27 -- and it all came down to the birthday call.

"Ashley remembered my birthday," Elizabeth said. "But I don't hold grudges against Mary-Kate forgetting mine. She was out of town! I should have just said my brother!"

Elizabeth turned 25 this past Sunday.

"Live" host Andy Cohen softened the blow for Mary-Kate by saying, "Ashley's in the lead today but tomorrow MK could do something amazing!"

Elizabeth added that she's close with all her siblings, including her brother.

"Mary-Kate's literally going to come home from her vacation and shoot me that I said that," she said. "She's in Jamaica."

She backtracked and said when on vacation, you rarely read the date, excusing her sister for not calling or texting.