Sorry for the late reply.
The marriage record of John & Mary is on www.rootsireland.ie/ in case you don't have it:
Date of Marriage:23-Apr-1865
Parish / District:CLONMEL
Civil ParishOccupation:KEEPER IN ASYLUM
SERVANTAge:Full Age (Over 21)
Full Age (Over 21)Status:Bachelor (Previously unmarried)
Spinster (Previously unmarried)
PRIEST: JOHN BALDWIN PP
GROOM KEEPER IN LUNATIC ASYLUM
Not sure how this one fits in:
Name:John RyanDate of Birth:
Date of Baptism:07-Nov-1848Address:Not RecordedParish/District:ST MARY'S PARISH, CLONMELGender:MaleCountyCo. Tipperary
Father:John RyanMother:Margaret KeatingOccupation:Not Recorded
Sponsor 1 /
Informant 1:William Keating Sponsor 2 /
Informant 2:Joanna Keating
I couldn't find a marriage of John or Lawrence to Catherine Schevers; closest to Schevers were Shanahan and Savage
No luck with Mary Keating with father James 1849 + - 01 years either I'm afraid
Surprisingly there are no Ryans or Keatings in Tipp in the 1851 Irish Census!
I don't know what sources you have used but the National Library has the R C registers free to search at registers.nli.ie/
There are baptisms and marriages for Clonmel St Mary's available but it's hard work going through them.