Hi there,
I don't really know anything about Luke Doolin, but someone left me a message on my Ancestry .co .uk site about Patrick Doolin, this if its the same one, was my Aunties Dad.
I do know he was born in Dublin and married Annie Walsh , my Aunts mother, as far as I know he was in the Royal Dublin Fusiliers and they had 6 children Julia, Bridget, Kathleen, Jimmy, Mary Margaret ( my Auntie Pat who's 86/87 yrs) and Richard. I think she told me he had a brother Charles and a sister Bridget that she knows of.
I will phone her or my cousin, to try and check some of the information thats been posted in reply to you.
Don't know if this is of any help, but will try to find out more for you, you could have a look at my tree on Ancestry, if you like.
All the best eita