The rest is the usual: flirting, pickup lines, and appearance compliments.
To do this faster, it definitely helps for a Sim to have charisma or some sweet love aspirations. Their relationship or marriage has to be a bit mature and the bar filled to at least 40% or 50%. Now, if you don’t know already, two Sims cannot try for a baby right away.
“ Try for Baby with” is an option for any of your teen Sims who are in a romantic relationship.