Yazanm, I thought that I might be able to see a logical pattern in the issuance of citizenship certificates to members of your family, but I have to admit that I cannot.
For example, the child of Son 1 (born 1935), who was born in 1968, was refused a certificate, yet the child of Son 2 (born 1936) was issued one.
For the grandchildren to have inherited Canadian citizenship, in addition to having had to be born before April 17, 2009, at least one of their parents had to have been a Canadian citizen at the time of their birth. Under the original Citizenship Act:
1) Your grandfather would have ceased to be a British subject and would not have inherited Canadian citizenship in 1947 if he became a citizen of any non-British country before 1947.
2) If he did not, and your father and uncles became Canadian citizens in 1947, they would have ceased to be Canadian citizens if they were living outside Canada on their 22nd (later changed to 24th) birthday.
So, if the three sons just became Canadian citizens on April 17, 2009, and were not citizens when their children were born (in 1966, 1968, 1970, 1974, 1979, 1980, 1981, 1986, and 1987), then none of the grandchildren should actually have been issued citizenship certificates.