@denversgray maybe because of your approach of mixing in friendly interactions, you're not achieving a high enough social context score?
What I mean is, it requires a certain level of social context - if you string a bunch of romance interactions together, you go from a casual conversation > suggestive conversation > amorous conversation > steamy conversation.
If you're weaving in some friendly interactions, you could be killing the romantic mood and dragging the conversation back towards friendly rather than romantic context.
For First Kiss to appear, it needs a high enough romantic context. Usually an amorous level conversation will guarantee it, but other things also boost your context score, like having a high charisma, so it can appear sooner than that depending on your sim.
Try doing exclusively romantic actions to see if it appears.
