Michael McMahon - missing information

Hi guys,  

I've never posted here before, so if I've not followed the rules I apologise! 

My great-grandfather's name was Michael Keane, assumed he was born in Clare, and he married my great-grandmother in 1924 whose name was Hannah McMahon and was from from Corncreagh. 

He eventually took over his wife's family farm, and our current farm, in Corncreagh. 

However, it is a mystery to my family and I as we cannot find a birth certificate for him nor any infomation for his family. All we know from the marriage certificate is that his fathers name was 'Thomas Keane' and that he was currently residing in Doonbeg.

Additionally, my family always claimed that he moved to Australia during the war but later moved back to Clare.

Any help would be much appreciated, thank you!

Órlagh x