Gamora's relationship status in the comics is rather complex. Sometimes she has brief romantic encounters, but no long-term, stable partner. It all depends on the particular comic arc and the creative direction at the time.
The main characters are clearly Peter and Gamora. Peter, also known as Star - Lord, is a charismatic and somewhat roguish character. Gamora is a fierce and highly skilled warrior. In this fanfiction context, they are the ones at the center of the story, especially with the added element of Gamora being pregnant.
Their relationship would likely deepen. The impending arrival of a baby would bring them closer together on an emotional level. They'd have to communicate more about their hopes and fears for their family. For instance, they might have long talks about what kind of values they want to instill in their child.
Another plot could involve them preparing for the arrival of the baby. They could be seen shopping for baby supplies in different alien markets. Quill would be clueless about most things, while Gamora has a more practical approach, leading to some comical situations.