My GG Grandmother Ruth Twiss was illegitimate. She was born in Haydock, Lancashire on May 18, 1851 to Eliza Twiss. The family story is that Eliza was a live-in servant at a manor house (possibly in Bryn), and the manor lord's son took advantage of her. Eliza was said to be "slow." There does not seem to have been a bastardy bond, or at least I can't find it. Her birth certificate lists her mother as "Margaret" rather than Eliza, but does not list her father. I've never seen the mother called Margaret anywhere else. Ruth's marriage certificate lists her father as Joseph Twiss. Eliza's parents were Joseph and Mary Twiss (nee Brown). So I think she listed her grandfather as her father, I don't know.
There is more to the story in that the father's parents supposedly sent him to Australia after this happened. I have no way of knowing if any of this is true.
I have had my DNA tested, and so has my dad. I was hoping to find clues that way, but I really don't know enough about DNA testing to know if that's possible. It seems like it should be...but a professional genealogist told me what I want to find out is impossible. But then he told me to buy his book, so I'm not too impressed.