You'd have better luck with a better posting; one that had dates, even approximate ones, and a spouse's name. Dates and spouses help identify people. Saying Robert was your great-grandfather helps a little. It leaves open a lot of possible years, however. Take two extreme examples, assuming most people have children when they are between the ages of 20 and 40:
1) You are now 70. You, your father and your grandfather are all the youngest (last born) children in their family. That makes your great-grandfather’s birth year (70 + 40 + 40 + 40) 190 years ago - 1812, born in George III's unhappy reign. Your grandfather and his brother went to NZ in a sailing ship, maybe during the Crimean War.
2) You are now 20. You, your father and your grandfather are all the oldest (first born) children in their family. That makes your great-grandfather’s birth year (20 + 20 + 20 + 20) 80 years ago - 1922. George is still King, but it is George V, not III. Your grandfather came to NZ after WWII.
Both of my examples are extreme. They are, as my dad used to say, "physically possible but highly improbable". You should not reveal the ages of living people, including yourself, on public forums, but you should give people some date ranges, especially if the surname is common.
The best way to distinguish between all those Adams is a spouse's name, especially if is is uncommon. If your grandmother's maiden name was Rogolinski, you have a definite advantage. If it was Smith or Jones or Morgan, you are still in a swamp.
Andrew's death certificate may have his mother's maiden name, if you can find it.