Each other
Incorrect : Each other love Reza and Rina.
Correct : Reza and Rina love each other.
Note: "Each other” cannot be used as the subject of a sentence. Formerly, "each other” was used when two people were involved and “one another” was used when more than two people were involved. But many writers now do not observe this distinction and use these two expressions interchangeably when two or more people are involved.
We can also say:
All the members of the family love each other/one another.