Who is Mami and Papi from The Dead and the Gone and what is their importance?

Mami and Papi are the Morales children's parents. Mami went to work at the on the night of the asteroid collision, and it is believed that she drown in the subway tunnels. Papi was Puerto Rico attending his mother's funeral a few days before the asteroid, and he hasn't been heard from since the day of the disaster. It is believed that Papi was killed in the tsunamis.