to be (to you)
Para serte sincera, nunca un ciego había querido irse de intercambio.
To be honest, a blind person had never wanted to go on an exchange program before.
— A primera vista (2014)
Quiero ser tu esposa y serte fiel.
I want to be your wife and be faithful to you.
— La dolce vita (1960)
Para serte franco, así es como sucedió.
To be honest, that's how it happened.