It often starts with a shock or surprise at the mpreg situation. Then, they gradually learn to rely on each other more. For example, Vegeta might start to show a more caring side that he usually hides, and Goku might become more responsible. They'll have to communicate more, sharing their fears and hopes about the future with the baby.
They might face the challenge of not being recognized by their past selves or other characters. Also, they could accidentally change things in a way that creates new and more dangerous villains. Another challenge could be dealing with the technology and power levels of the past, which are much lower than what they are used to.
The fanfiction might make their relationship more equal in a different sense. Before, there was always a bit of a power struggle between them. But as mates, they have to respect each other on a whole new level. They would have to consider each other's feelings and opinions more. For example, when making decisions about how to face a new enemy, they would have to consult each other rather than just going with their own instincts like they used to.
Vegeta would likely be arrogant towards Chibi Goku at first. He'd see him as just a puny Saiyan child. But Chibi Goku, with his innocent charm, might start to break down Vegeta's tough exterior. For example, Chibi Goku could offer Vegeta some of his food, which is a very Goku - like gesture. Vegeta would be taken aback but might slowly accept it. Then they could start to have simple conversations about their Saiyan heritage.
Bulma could be involved. Since she has a relationship with Vegeta and is friends with Goku, she might try to mediate between them when Goku snaps at Vegeta. She could be the voice of reason, trying to calm both of them down and make them see each other's point of view.
To draw a manga face, begin by defining the jawline and cheekbones. Then, create unique eyes and eyebrows that convey the character's mood. Don't forget to add some light and shadow for a more realistic look.
You start with sketching the basic shape of the head, then mark the position of the eyes, nose, and mouth. It's all about getting the proportions right.