Gerrard Irvine

Gerrard left Ireland in 1855 bound for Australia on the ship "Kate",  on his immigration paperwork he listed his father as James and mother as Ann at Rockfield.  On his marriage certificate his father is listed as Richard Irvine and mother as Ann Mack.  Is his father James or Richard?  I seam to have hit a brick wall with this and don't know where to look or who to look for.  

 

Sheryl