Sorry, but I don't have any specific info on the Langley family - just trying to help you out, if I can.
Do you know where Thomas Langley (father of Samuel snr) was from? I had a look at Griffiths Valuation, and there were only 2 Thomas Langley's in the whole of Ireland - one from Mayo and one from Tipperary. If one of these is "your" Thomas, you have a good chance of finding his marriage cert - unless you already have this info?
Also (again, unless you already have the info), you might be able to find a baptism cert for Samuel snr. in the local Parish records, and perhaps other siblings.
Who was Annie Fitzpatrick's father? Do you know where he was from? You should be able to find him on Griffiths if you have that info. Unfortunately, Fitzpatrick is quite a common name, and it will be difficult to pinpoint him without at least a county to go on.
Maggy is normally short for Margaret, so maybe the registrar just got it wrong in St. Andrews, and mother of Kate was Anne, and NOT Mary - it happens, and I have proof of it myself, unfortunately! But if you get Kate's state birth cert, it will give you her mother's correct name.
Not sure what else I can tell you, but again, good luck in your search!