How is "Unrequited love" a part of A Midsummer Nights Dream?

The opening of the play is filled with unrequited love; Hermia and Lysander are madly in love and hope for marriage. Hermia’s dad, however, wants her to marry Demetirus, who wants to marry Hermia

Then we have Helena, Hermia's bestfriend; she is in love with Demetrius, who does not return her love.