Romantic interests

[SecretBoy]

Today I discovered some information. My two sims in my casual game were good friends and sat on the couch. I found the option to cuddle up and I did that, and then I found the (Kiss) action. They did it and are now RI's!  A quicker way to do it instead of doing all the actions standing up

[Lysita]

A kiss always make two sims become romantic interests if they aren't already, or aren't any of the other partner relationships(boyfriend/girlfriend, fiance, husband/wife).

[ratchie]

Yeah I discovered that quite a while ago. The only problem is if you want to get them to boyfriend/girlfriend status you still have to go through all of the romatic socials.
If you want them to just be romantic interests the quickest way is to give one of them the inappropriate trait and they will have the option to kiss a complete stranger upon first meeting. Once they kiss they will be romantic interests.

Rachel