At the end of the day, Shepard can romance any of the folks aboard the Normandy in Mass Effect 3 and still have a chance at rekindling their relationship with Kaidan, Ashley, or Liara later on. In Mass Effect 2, Shepard will have a chance at romancing characters that weren't available in the first game, such as Garrus and Tali, as well as some new faces like Miranda Lawson, Jack, and Jacob Taylor. RELATED: Mass Effect 2: How to Romance Miranda In all instances, Shepard will retain a photo of their love interest in their quarters, despite having essentially broken up. Kaidan and Ashley will be upset with Shepard for joining Cerberus while Liara is busy dealing with Shadow Broker business. However, during Mass Effect 2, they'll be unavailable for various reasons. Both male and female Commander Shepard have two options each: either Ashley or Kaidan, depending on player gender, and Liara. Liara T'Soni, Ashley Williams, and Kaidan Alenko are the characters introduced in Mass Effect 1 that are romanceable from the get-go.
Many characters are handled on a case-by-case basis, such as Miranda Lawson, whose consequences can be catastrophic. Some players might be wondering what if they can start a new relationship after romancing a character from the first game, or if it will have consequences further down the line. The choices between Mass Effect, Mass Effect 2, and Mass Effect 3 carry over, and this includes romances.