William b 1905 doesn’t appear on the WW1 record, so he must have died, also 1911 says 5 children born, 3 surviving, accounted for in the 1911. No William
The other one who died must be the 1910 Thomas
Birth
AMBROSE, MICHAEL JOSEPH POWER
GRO Reference: 1879 D Quarter in MANCHESTER Volume 08D Page 297