2015 was a busy year for the Girls' Generation members. They made a successful comeback with Lion Heart and hosted a concert. Girls' Generation TTS recently released the Christmas single "Dear Santa." 

In addition, six out of the 20 most popular Korean celebrities on Instagram in 2015 were Girls' Generation members, which proves just how popular the girls are. 

In spite of their achievements in work, some of the members' love lives didn't do so well. 

Earlier in 2015, five Girls' Generation members were happily in a relationship. By the end of the year, unfortunately, four out of the five have split with their boyfriends. Here are the 4 Girls’ Generation members who split with their boyfriends in 2015. 

1. Nichkhun and Tiffany

2PM's Nichkhun and Girls' Generation's Tiffany dated for over two years, the longest in this list, before they split in May 2015. 

Even before the couple publicly announced the relationship, 2PM and Girls' Generation fans speculated about the relationship due to Nichkhun and Tiffany's matching accessories. 

2. Baekhyun and Taeyeon

EXO's Baekhyun and Girls' Generation's Taeyeon's secret date was uncovered in June 2014, when Dispatch revealed photos of the top stars kissing in a convertible one summer night. (Click here for more details on how it happened) 

"Baekhyun picked Taeyeon as his Ms. Right ever since his debut, and Taeyeon thought that was so adorable of him," an acquaintance said in an interview.

In October, the first in-company couple from SM Entertainment split, saying their busy schedules made it difficult to continue the relationship.

3. Im Yoon Ah and Lee Seung Gi

Singer-turned-actor Lee Seung Gi and Girls' Generation's Yoona decorated the front page of newspapers on New Year's Day 2014, when Dispatch released photos of the top stars secretly visiting each other's homes.

The couple confirmed their breakup in August, adding that they decided to remain good friends instead.

4. Yuri and Oh Seung Hwan 

Baseball player Oh Seung Hwan and Girls' Generation's Yuri quickly acknowledged their relationship after paparazzi photos were released in April. The couple confirmed a split in October. 

When Yuri's breakup news spread in October, Girls' Generation's Soo Young and actor Jung Kyung Ho confirmed that they are still dating. 

See where the SM Entertainment's top stars like Super Junior, Girls' Generation, SHINee and more got their start in I AM:

What do you think of the Girls' Generation members' former boyfriends? Tell us in the comments below!