"Porodica" is closer family (mom, dad, brother, sister), "rodbina" is used for cousins, aunts, uncles etc.

Porodica (close family) is your close family (mom, dad, brothers and sisters). Extended family contains: grandmother, grandfather, grandchildren, aunt, uncle, .... Close + extended family contain rodbina - relatives. I hope I was clear to you with this answer. If you want you can look at my profile and I can teach you my native language.

Let's analyze from the point of view that is the simplest one - first and second graders of primary schools. So, we teach our children that the family (porodica) are mother, father and our brothers and sisters. That is by the book and official theories. However, we often live in expended families which usually include our grandparents. Relatives (rodbina) are other people related by blood (such as cousins, aunts...) or by law (sister-in-law...).

родбина је шира породица....родбина може бити фамилија....фамилија може бити породциа....тако да је међународни (интернационални) израз фамилија: и родбина и породица...тј. и једно и друго.

Porodica is your close family, including mother, father, brothers and sisters, but sometimes, it can relate also to grandparents (for example if you live together with your grandparents too). Porodica is actually everybody who is living under the same roof. Rodbina (or familija) is your larger family. Rod, rodjak = cousin.