You can try the following by Pescado:
No Instant Love - **If you don't use Inteen**
Romance mod
You can download the AL version from
here.
The Sim Blender has the options to adjust the types of relationships your Sims have with each other plus there's ACR that does almost what you have in mind if you don't have ACR already. You can check out
ACR at Simbology if you haven't so.
If I do come across another relationship mod, I will add more info.