If you pick Dont be, youll pick Liara, and a Romance with Ashley will be ceased. If you pick Cant I have you both? at any time, BOTH of them will be upset with you and youll be locked out of a Romance with Ashley.
Can you avoid romance in Mass Effect?
Players can also avoid romance by refusing to talk to Liara and either Kaidan or Ashley at all during the downtime between missions. While this causes them to miss some backstory for each character, it will prevent a romance from triggering.
Is Kaidan a good romance option?
Kaidan is unique among the Mass Effect 3 Romance options because he is one of only three who can both be Romanced for the first time in this game, or have a Romance from a previous game continued. While he was only available to Female Shepards in the original game, in Mass Effect 3 hes open to Male Shepards as well.