Did Martin Luther King, Jr. or Malcom X have children, and were they friends?

Martin Luther King, Jr. and Malcolm X both had children.

King had four children with his wife, Coretta Scott King— Yolanda Denise, Martin Luther III, Dexter Scott, and Bernice Albertine. 

Malcolm X had six children with his wife, Betty Shabazz— Attallah, Qubilah, Ilyasah, Gamilah Lumumba, Malikah, and Malaak. 

Reverend King and Malcolm X only met on one occasion (March 26, 1964) and did not maintain a friendship. The two felt that while they had similar aspirations for racial equality, their methodologies almost entirely prevented them from working together. Leading up to the assassination of Malcolm X, the two were increasingly in contact and there may have been potential for King and Malcolm X to unite their religious and sociopolitical influences. Unfortunately, this potential was not realized in their lifetimes. 

As for whether the children of Reverend King and Malcolm X were friends, Yolanda King and Attallah Shabazz met for the first time in 1979 and went on to collaborate on a theatrical production. It is possible the other King and Shabazz children met or corresponded on some occasion, as their fathers both died fighting for civil rights, but there is nothing to suggest friendship between any of them.