Just one example of the process I went through in one case. I was in contact with somebody who is a DNA match (we are 8th cousins once removed) and she mentioned that what she had found on the FamilySearch website differed from what I had mentioned to her.
She said:
"I just looked on FamilySearch and it has Richard Rodway as son of William Rodway and Ann Cox. Do you have sources to correct that record?"
My reply (I'll leave out the links)
We're looking for the father, Richard, of the Mary Rose Rodway who married Henry Stinchcombe in 1872. There are three possibilities for her father; one is Richard born in 1830 in Hawkesbury to William and Ann, another is Richard born in 1825 in Gloucester to Thomas and Elizabeth, and the final one is Richard born in 1828 in Cricklade Wiltshire to Rose.
When Mary Rose married on 16 Jun 1872 the Marriage Register showed that she was a Minor (ie under the age of 21) so she must have been born after 16 June 1851.
The Civil Registration Birth Index shows that she was born in Q3 (Jul-Sep) 1851 so she married a couple of months before her 21st birthday.
Ancestry doesn't record it but on FindMyPast it shows that her mother's maiden name was Stokes. So we are looking for a Richard Rodway who married a woman named Stokes sometime before 1851.
To take things backwards from there, at the time of the 1871 census, Mary Rose was working as a housemaid in Cheltenham but there is no record of the rest of the family in 1871.
In the 1861 census Mary Rose was shown as living with her father Richard, mother Mary E and brother Stephen G in Cheltenham. Richard was 33 (so born approx 1828) and he gave his place of birth as Cricklade, Wiltshire
Then in the 1851 census taken just before Mary Rose was born, Richard was shown as 23 (so born approx 1828) and is shown living with his wife Mary E as lodgers in Littledean. He again gave his place of birth as Cricklade, Wiltshire
The Marriage Registry shows he married Mary Emily Stokes on 10 Apr 1850 in Tidenham. The name of his father is shown as Stephen. In reality, Stephen was his grandfather (Stephen had already died in Cricklade, Wiltshire in 1819.)
In the 1841 Census Richard is shown as 12 and living with his grandmother Mary and aunt Diana in Cricklade Wiltshire.
There is then a record of the baptism of Richard on 19 Oct 1828 to Rose Rodway in Cricklade Wiltshire. There is no record of the father.
I think the fact that he gave his place of birth on two censuses as Cricklade and that when he married he gave the name Stephen for his father is indicative that it was this Richard that was the father of Mary Rose.
The other possibility was the Richard who was the son of William and Ann. He was born on 8 May 1830 in Hawkesbury and then baptised on 30 Jul 1830 in the neighbouring church in Wootton under Edge
Then in the 1841 census he is shown living with his older half-brother, Charles, in Hawkesbury. There is no record of him in 1851 - his brother Charles had married by then.
Then in 1859 there is a record of the burial of a Richard Rodway in Hawkesbury who was aged 29 (so was born approx 1830).
I think it is very likely that the Richard who was buried in 1859 in Hawkesbury was the son of William and Ann.
The other possibility was the Richard born in 1825 to Thomas and Elizabeth. He married Sarah Ann Baker in 1863 in Gloucester.