Hi Amanda, I should be getting through some deadlines but this has intrigued me so I had a quick dig around - I notice you've a tree on Ancestry and have researched your grandmother's near relations.
Checking the BMD's up to 1921 here are some other possible siblings of your grandmother in addition to the ones on your tree (infants with father Jayes, mother maiden name Price):
Elizabeth Jayes, December qtr 1913 Birmingham 6d 443
May Jayes, December qtr 1918 Birmingham 6d 287
There are other children after 1921 who had father Jayes and mother maiden name Price, its possible Abbot John Jayes remarried another member of the same family after his wife's death. That's exactly what happened in my family, John Griffin, my Stour Street ancestor married Alice Hern, then after she died after giving birth to 3 children he remarried within 6 months her younger sister Ann, who had a further five children by him, the first born exactly 9 months after her sister died!
Also you note that Gladys May Jayes married Charles Kelly. Checking birth entries for children born thereafter with father surname Kelly and mother maiden name Jayes brings up two: Ronald K Kelly (Sept qtr 1939 Birmingham 6d 221), and Brian J Kelly (June qtr 1942 Birmingham 6d 309) - they may very well be still alive if you can trace them.
A potential marriage for Brian J is March qtr 1959, Birmingham 9c 277
Ah, must get back to work! I hope this is of help.
John