Re: [request] committal or fathful trait

The opposite trait to non-committal in terms of relationships would be family oriented, romantic, or even jealous (since it gives boost to being around significant other). Non-committal isn't just about relationships but also about jobs and all other aspects of the Sim's life. A non-committal Sim (or person) wouldn't necessarily cheat, they just wouldn't want to be in the same relationship for a long period of time. Same goes with being in the same job, doing the same hobby etc. 

Edit: Although I would like to add that a non-committal Sim (or person) can also be romantic, family oriented, and jealous...