Question

Marco: ¿esa es la foto de la boda de tus padres? marta: sí, ellos son ______ padres.

Answer 1

depending on who Marta is talking about, if she is saying the parents are hers it would be "mis" if she is saying that the parents are Marcos then it is "tus" but i am pretty sure Marta is saying "mis"

Answer 2

"mis" should be in the blank spot.   ellos son mis padres.