Hi Sue,
This may not be Arthur. My mother wrote on the back of the photo and she was not really a reliable source lol. My grandmother (Gwen) told tall tales for fun sometimes and it is highly likely that this has happened.
For years everyone thought he was Albert because Nanna said so, but she was teasing my mother and finally when the timing suited her she said, "no I just said that because he looks like an Albert". So my quest is not made easy ...bless her little cotton socks. 
Lena had 3 bothers
- John James Baker who served in Egypt WWI
Kim
I have had a look at the service history of John James BAKER
The physical description fits the man in the photo (but it is vague)
The age of John James, 26 to 28 years actually suits the man in the photo . I think the chap looked a little old to be Arthur.( b. 1893)
However I do not see an entry of LEAVE on the record which would provide the opportunity for the photo to be taken.
Perhaps others will read it better than me.
If it is a studio portrait, some arrangements would have been made in advance.
The twins are not yet 2 years in the photo I believe.
I am not able to assist with their exact birth date. Are you at all able to help with the month of Gran's birthday?.
It may help if you can find it.
Is there any studio identification on the back of the photo?
Sue
PS
Glad you got the hang of reply
