I could not find an exact birth for Richard Jenkins, as there are 2 possible candidates from Llanidloes registrar which are
1790 Richard Jenkins, bachelor, marries Mary Morris, singlewoman, at Llanidloes Parish Church, and both are "of the parish". Married by banns on 24 May 1790. In presence of Evan Evans and Lewis Richards.
Llanidloes St Idloes Church
Flannel Mill in Llanidloes
1797 John baptised, son of Richard Jenkins and Mary has wife on 19 Mar 1797 at Llanidloes. I need to further check Llanidloes register for sibblings. IGI only runs from 1813.
There is a re-marriage of Richard Jenkins, widower, to Hannah Rowlands on 17 Oct 1818, which may or may not have been he. It would appear that this marriage produced the children on the chart on Hannah Rowlands page. Certainly Mary is the product of that marriage, and the mother of Mary is Hannah Rowlands. The other baptisms in the parish church do not give the mother's maiden name, but appear to be this family. Richard Jenkins is dead by 1841 census, so little more can be gleaned about him. One has to take a view on how many Jenkins families there are in Llanidloes and how many Richard Jenkins, then try to tie "my" Richard to "Hannah's" Richard.
Family fan chart