As with the original Mass Effect, there are many romantic relationships that Shepard can have with members of his crew. In fact, the number of these has been vastly increased.
For playing as a male Shepard, you can have a full-blown romantic relationship with:
A female protagonist can have such relationships with:
A Shepard of either gender can have relationships with:
- Kelly Chambers
Note that relationships with these last three do not inhibit proper relationships with the previous six. You can do these at your leisure, but they do not give you the Paramour achievement.
To convince a crew-member to join your Shepard in a romantic relationship, you need to work at it after every major mission. Completing the loyalty mission for that crew member will go a long way to helping, and picking Tali over Legion or Miranda over Jack (or vice versa) also is a great show of your affection. Speak to Mordin for relationship advice, as he has much to offer!
Eventually they will express their desire to be with your character. At this stage, when you go to the Omega 4 Relay, they will pay you a visit. Should you remain faithful to them, you can then invite them to Shepard's quarters (where Kelly Chambers will dance for Shepard). Note that while it is attractive to try and romance every possible crew member in the game, this will have repercussions for the next game in the series.
You can break up with a crew member, and should you wish to pursue a relationship with another character, you will be forced to make this choice. Note that once you have split up, you cannot reignite the relationship.
Note that with Jack, you must turn down her initial request for casual sex, or she will refuse to speak to Shepard again. Work at the relationship with Paragon motives and she will visit Shepard before reaching the Omega 4 Relay.
Note that with all the romance options, you should pursue them as much as possible before the Omega 4 Relay, and with Kelly Chambers before the Reaper IFF. Much of the progression in the relationship happens during the Suicide Mission, and cannot be easily replicated afterwards. After the Suicide Mission, you can update romantic interests to Shepard's quarters.
Note that if you proceed to have sex with Morinth, it results in a Critical Mission Failure, and you will have to load a recent save.
Note that Samara requires a Paragon to convince her of romance.