All that can presently (July 2023) be gleaned about
The Hopkins Sisters from sheet music covers and by Internet searching is that they were presumably American actress/singers who have been featured on 2 works published between 1914 and 1915.
Their portrait on the left is taken from is
Down at the Barbecue (1914) music by
Ernie Erdman, words by Roger Lewis and published by
Will Rossiter, Chicago, Illinois, USA.
Surfers are welcome to contribute any further information about these performers.