Featured Roughly when were these photographs taken?

Same sitting as with your great great grandfather. Notice the dress, bare feet and hair.

 

Yes you're right. Given the oval shaped photo I think I can confidently say it's a late 1910s photo.. I've seen a few from that era and later. Would you agree?

 

I thought you dated the one with your g.g. grandfather as 1919. So this would be the same.

 

Hi, yes it is but just wanted to show those extra photos incase lol

 

Out of interest, does anyone know when these type of photos came into existence and how long they were around for?

 

You said that one was a postcard, correct? If so, real photo postcards (RPPCs) generally started being used in the very early 20th century and the type in your post continued to be used for a long time... at least until the 1930s. Photo postcards still exist today, but are different.

There are several pages online that give some history of real photo postcards. However, I have never seen an online site as thorough as the histories in a couple of published books:

Real Photo Postcard Guide: The People's Photography, by Robert Bogdan and Todd Weseloh (Syracuse University Press, 2006).

As We Were: American Photographic Postcards, 1905-1930, byt Rosamond B. Vaule (Boston, David R. Godine, publisher, 2004).

The second book is a social history, but both of them include social practices related to the popularity and use of the cards. The first book has more historical facts in it, and also includes information similar to what can be found online on how to date postcards partly by what's on the back, etc.

If you are interested in RPPCs, I can recommend both books. I would recommend reading the first one first.