can non-mahram family members casually mingle in the same room, but seperate couches? I personally don't feel comfortable with a non-mahram even hearing me laugh or talk (alhamdulillah I am wearing proper Hijab and Niqab but not all women present wear Hijab or Niqab) What is the ruling on this?

Ustadh AbdulAziz al-Haqqan

You laughing and joking and showing your femininity is not allowed therefore such things should be avoided. What is allowed is formal respectful salam or if there is a need to speak accordingly, this is a brief answer and I recommend that u look into it more from the sayings of the ulama.