Carl and Sophia are indeed deceased in The Walking Dead comics. Their fates were determined by the story's progression and the challenges the characters faced in that post-apocalyptic world.
Well, a plot might involve Carl and Sophia finding a group of survivors who have a different way of living. They have to decide whether to stay with this new group or continue on their own. It could also be that Sophia gets injured and Carl has to find medicine for her, leading him into dangerous situations where he has to face not only walkers but also some not - so - friendly humans.
In a scenario where they are constantly on the run, their relationship could develop into a very deep bond of trust. They rely on each other for survival, and this could turn into a love - like relationship over time. For example, Carl might sacrifice his safety to save Sophia from a walker.
Unfortunately, Carl did die in The Walking Dead comics. It was a sad moment for fans. His death had a big impact on the storyline and the other characters.