The human limbic system carries out emotions. This is located in the temporal lobe of the brain (by your temples!). The brain is complicated and this system is made up of many parts. There isn't one part of the brain that operates independently of other parts. There are many chain reactions. The center of emotional processing is the amygdala (it is a very tiny but powerful part of the brain that is the size of an almond and may be responsible for our nightmares); however, the amygdala receives a lot of input from other parts of the brain and it influences our emotions.
Our memories tied to emotions influence how we process emotions over time. Brain functions such as decision making, attention, anxiety, and memory influence how we process emotions which is why we all have a unique experience of love.
What can be romantic to one person may be viewed as negative to other.