Welcome to Rootschat.
Richard does not seem to name Children Robert/Martha.
Children were to RICHARD/MARY;
Baptisms;
Ann MANDERS, 07 Mar 1794,Wrawby : St Mary
Thomas MAUNDERS, 09 Aug 1795, Cadney : All Saints (poss buried 4 Jan 1816 age 19)
John MAUNDERS, 18 Apr 1798, Cadney : All Saints
William MAUNDERS, 01 Mar 1801, Cadney : All Saints
Elizabeth MANDRES, 10 Jul 1803, Cadney : All Saints
As you say Rchards 1821 burial has him as age 56 (1765)
Having said all that the only Richard to be found on-line is the one Schoch (Richard) posted.
Hopefully someone else can come up with something for you
