When "Captain Forward and Lieutenant Back" went forward in time:

 When two U.S. Air Force officers were sent forward in time in 1992 there was a rumor that the human race went extinct in the last 20 years of this century. However, no one specifically had gone forward on a mission in time yet from the U.S. government or the United Nations to research this fact of life.

So, when they found out that this was true they came back and gave their presentation to a secret group of U.S. Generals and then the secret Group of United Nations representatives which is how things are done on this level now here on earth since the United Nations was formed after World War II as a way to avoid conflicts like World War I and II in the future.

So, beginning that year the governments of the world secretly began planning how to "thin out" the human race enough so we didn't go extinct and thereby they began altering the time line enough so everyone didn't go extinct by 2100 AD here on earth. So far at least this has been successful.

However, global climate changes likely will still reduce mankind down to less than 1 billion by 2100 AD.

This appears presently to be pretty certain.

So, if you want your family to be one of the families that survives past 2100AD you need to begin planning how your family is going to survive past 2100 AD now if possible.