Murdoch's parents died in 1917, so maybe lightoller visited them. I've read a post from inger that moody visited lightoller, also pittman was close to moody, even writing to moodys sister Margaret. it seems all titanic officers were close to each other and to each others family members.
I don't know where Murdochs mother came from, but I did presume both of his parents were Scottish. I've never read anywhere that his mother was from Ireland. Maybe you got confused with officer lowe? He was from wales, close to Ireland.