According to this link that is from one of the profiles in the line:
https://biography.wales/article/s1-GRIF-PEN-1300
GWILYM FYCHAN (c. 1420 - 1483)
The son of the marriage of Gwilym ap Griffith and Joan Stanley,
The mother connected to this Gwilym Fychan is correct but the father is, as noted, Gwilym ap Griffith rather than Gwilym ap Gruffudd, of Penrhyn.
?
Thanks in advance for any clarification.