In North Antrim/Derry the surname Gemmell is also Gamble 
Registration of births in Ireland started in 1864 and the first complete census for Ireland is 1901- all too late to find this particular family.
I'm equally in the process of tracing back the lines from my grandmother Agnes Howard Gemmell (Coatbridge Scotland). Just to say that in using Scotlands People website and the various documents therein (births, marriages, deaths and census) and ensuring each family is linked to the previous one I've come across as spellings: Gemmell, Gemmel, Gammal, and Gamble. So one has to be patient and dig, dig, dig. Just a wee tip - if the town of birth is known (often from the census) but one can't find the records try just the year(s), town name, and first name: that's how I finally found my great grand father's birth record - recorded under the name Gammall (but written as Gemmell in the register). Happy hunting