Some people can go more into detail about that stuff but as far as I know, you have to code it with a choice.
In your choice, when they pick the interest they want, under the choice you put something like @Char stands screen center or a specific spot just to show them if they pick a gril/boy, what they would look like, and you also have to flag it.
Keep in mind, ive never done a choice like this so I may be wrong.