I agree that Charlotte Ditzler and Hugh Ditzler are somehow related.Since reading your theory about Charlotte being a pen name, I've collected several illustrations by both Hugh Ditzler, Charlotte Weber Ditzler, and even found one by Edna Ditzler.The signatures look very similar in all cases.
Charlotte seemed to illustrate ladies magazines, Edna illustrated political Satire (Judge Magazine), while Hugh did more serious work (Spanish American War, Navy Archive books, Harpers magazine, etc.)
Interesting too that Hugh's wives names were Charlotte and Edna.After their divorce, I did locate Charlotte on a Census between marriages.Her profession was listed as dress designer.So, his wife, Charlotte, could have had the artistic skills required for illustrations although I have never found her listed anywhere other than the magazines themnselves.Also, I'm not sure where her entire name (Charlotte-Weber Ditzler) fits in.Hugh's middle name was Witter which is a family name.
As a side note, his sister Wenonna (Winnie) studied art in Munich for several years around 1893-1903 although I don't think I've seen any of her work.Hugh had an art studio there for a while but seemed to travel between there and New York.(and Tampa and Cuba during the war.)She returned to Hinsdale and raised a family.