Hello Linda,
Had a look in the Hawarden Parish registers for Richard and Thomas. Are you sure they lived in Monkard or could it be Mancot?
I found Thomas's Baptism, 28 Feb 1812, son of Richard Bithell & Mary (CARN) of Mancot. Born 22 Jan 1812.
Also, Baptism 25 Sep 1796, Richard Bithell son of Richard & Mary (CARNE) Saltney.
20 Oct 1805, Edward Bithell son of Richard & Mary (Carn) Mancot.
Burial, 8 May 1810, Edward Bithell son of Richard & Mary (CARNE) Mancot, Age 4 Years.
Marriage 14 Dec 1790. Richard Bithell & Mary Carne Both of this Parish (Hawarden) Witnesses, Samuel Coppack & W Deakin.
Are you sure the Richard you have born about 1786, is not Thomas's Brother born 1796 and Richard & Mary Carne their Parents. I could not see a Mary Welbank.
I hope this hasn't confused you.
Paul.