I think part of my reply to you was confusing.
You said that Richard's father was "Abraham Sadler" who died in 1768. I think you probably meant "was William Sadler who died in 1768". Am I correct?
I have the evidence from England Births & Christenings 1538 - 1975 which seems to indicate the following:
William Sadler born May 1663 had a son named William who was born in May 1688. He married Elizabeth Firby on 31 Oct 1711. Elizabeth's husband is then known as William jr in the documents pertaining to the births of their children (William (b 1712 and only lived a few days), William (b 1716), Mary (1730), John (1731), Thomas (1733 who only lived a few days) and Thomas (1738). William (b 1716) married Mary Geldard on 17th August 1740. They had four children: Richard(1740), Thomas (1743), Elizabeth (1746) and Sarah (1749). Richard married Hannah Strother on 23rd March 1763 and Abraham was one of their children. I have seen some information indicating that one of Richard and Hannah's children was Charles but I cannot find any documentation relating to this. Richard and Hannah had nine or 10 children depending on whether Charles was one of them.
I have all this in my family tree which is not on line. I have evidence of the various connections saved in a MS Word document but I cannot send it in this format on this site. I could try to convert to a jpeg format but would need to create about four different files. Let me know if you would like me to do this and I will send them in a few days time.
Best wishes.