However, when the sides met at Gelligaled Parc early in the season, it was Rhydyfelin who inflicted the only league defeat to date on their hosts.
Rhydyfelin have seen off challenges from Llantrisant, Loughor, Rhiwbina and Rhymney to reach this stage, with a late try try by outside half Lewis Smith sealing an 18-13 quarter-final success over Llantrisant taking them to the last four.
Ystrad Rhondda, beaten semi-finalists in 2012, defeated Felinfoel in the quarters 28-5, crossing for five touchdowns, Kenfig Hill, Treorchy and Merthyr and they will be keen to take revenge for that lone league defeat.
Cwmllynfell have reached this stage after four away ties against Brynamman, Bryncoch, Pontarddulais and the quarter-final at Kidwelly which they won 22-13. Their only home tie was against Builth Wells so they will be glad to play a semi-final in front of their own supporters with the visit of Heol y Cyw.
The One East side has knocked out Pencoed, Fairwater, Penallta and Pill Harriers, 23-11 in the quarters, to offset a difficult league season.
Cwmllynfell should start as favourites as they lie in second spot in One West while their visitors have already lost eight league matches and stand 9th in One East.
Ties to be played weekend of April 13
Cwmllynfell v Heol y Cyw
Rhydyfelin v Ystrad Rhondda