Very odd Common Ancestor / Thrulines match

[LizzieL]

I have a DNA match of 7cM with C. Ancestry tells me that C and I are half 5th cousins once removed, and that our common ancestor is my 4 x great grandfather Thomas Child. Looking at the relationship tree on Ancestry, it has my 3 x great grandmother (Esther Child) as the half sister of C's 4 x great grandfather (William Attfield).
Six Ancestry members trees are cited as source for Thomas Child being William Attfield's father. One is a private tree, but if I look at the other 5, none of them say that WA is TC's son.
They all say that WA is the son of Thomas Attfield and  Elizabeth Rampton.
So how has Ancestry invented this relationship?

[Gadget]

They use any trees that are in any way plausible. If they don't fit your tree after researching, ignore them.

[LizzieL]

But the five trees aren't anything like plausible. The only thing that matches is that both my ancestor (Esther Child) and C's ancestor, had parents called Thomas and Elizabeth and were born in Surrey (different towns) in the 1740's. Only one of the five trees have anyone with the surname Child, but they are from York and not directly connected to their Attfield line. I have no Attfields in my tree.

[Gadget]

Their plausible is not our plausible, Lizzie 

Add - I did say 'in any way' and you seem to have identified it!

[phil57]

But the five trees aren't anything like plausible.

That sounds like many Ancestry trees. If any of the trees are identical, they've probably been copied wholesale with no checking or any research. But Thrulines has no way of knowing what is plausible and what isn't. It just attempts to recognise individuals in different trees who may be the same person, and extrapolate their tree lines to create a possible link between you and a DNA match. Thrulines are hints, not facts. If, on investigation, you discount it, move on

[Flouncylicious]

Ancestry trees are definitely to be taken with a pinch of salt. I sometimes look at them, but validate anything plausible with my own in depth research. Most of time this disproves them. For example, for one of my brick walls there are several identical trees which have a mother who was born over 20 years after her son's baptism...

[Biggles50]

The Common Ancestor route between you and your match can be all over the place it is “Cobbled Together” via multiple Ancestry Family Trees, and we know how good those can be.

Every werk I check ours and my Wife has a new cM match via Common Ancestor the trouble is the James A who Ancestry says is the Common Ancestor his daughter Betty leads to my Wife does not fit in the shared matches line.

The shared matches line has the one below James A called Elizabeth and in the tree that Ancestry has used Elizabeth’s has Father is Joshua D, and in this tree has the documents to show her Baptism plus she was born 16 years after Betty in a different Town and her marriage lists Joshua as Father.

As it is James A is the Common Ancestor to three other DNA matches that we research and have linked to in my Wife’s tree so we are sure her tree is correct.

[Petros]

Indeed many Ancestry trees are questionable. Some have 12 year old brides having children soon after marriage!
This week I was filling out some details of one line of 5th cousins and found many trees intermingling details of two William Moorcrafts from Kent, born in 1823 and 1829, marrying two different Mary Anns. Some had all children of the two couples assigned to one set of parents while many had the earlier birth date, and village, for the younger William despite all evidence to the contrary from the various census!

[LizzieL]

This week I was filling out some details of one line of 5th cousins and found many trees intermingling details of two William Moorcrafts from Kent, born in 1823 and 1829, marrying two different Mary Anns.

But at least you can see the connection and sort out the two families. I have an ancestor, William Carr, who married a Sarah, his brother Thomas also married a Sarah. The two couples had children over the same time period in the same village. They duplicated many of the names of their children. I have a lot of thrulines which show descent from my Sarah (and William), but are really from Thomas and Sarah. Easy to see where the mistake lies and sort out the real relationship with the DNA match.
Another common problem is trees muddling the father of my 3 x great grandmother with her much older brother, which also gives a relationship one generation out to my DNA match. Again the match is associated with the right line but not quite correct.
But the connection between William Attfield and Thomas Child really stumps me, especially as none of the trees given of sources have this erroneous relationship.