DNA I manage has hundreds of matches showing as maternal

[Penelopej]

Hi,  I manage a person's dna on ancestry who is related to me on his paternal line.  His grandfather was the fathered by the brother of my great grandfather not who he had thought.  We have many matches proving this.  He has over 700 4th cousin matches .  Many many of them are through his father's mother's line.  They keep showing as maternal.  I know I can change them to paternal, but there are hundreds of them. I have put the matches that are also on My heritage onto DNA painter and many of those matches are often in the same place as my link to him and the others I know are through his father's line.  His actual mother's line has only a handful of matches and none of them are more than 20 cm.  So now I am wondering if he doesn't have another secret lurking in his tree? 
His father's mother shouldn't be showing as maternal unless his mother was actually related to them?  I hate to ask him as he has already had one surprise.  Thanks

[Jo6100]

Is this on Ancestry? Have you checked that he has allocated his dna to the correct parent on the ethnicity inheritance page?  There is an option to edit and change the allocation if it’s simply mislabelled mother’s side as  fathers which should correct all the matches also.

[familydar]

Another thought - you've not accidentally attached the DNA results to his father rather than your friend?

Jane :-)

[Penelopej]

His matches to me on his paternal line are from many different people's tests so I am 100% sure that that is how I am related to him.  The weird thing is that of the 760 4th cousin and closer matches two names make up the vast majority of the shared matches and they are his paternal grandmothers line.  His mother's line has about 30 matches of which only a small number over 20cm and none more than about 30cm.  She was born in New Zealand but her parents were English and she went back to England to marry then came back to NZ.  Her parents were actually first cousins so I thought this would magnify the number of cm to that line.

[Biggles50]

DNA is inherited in a random manner, and this increases as generations go by.

When “Cousins” marry, irrespective of their generational distance this in effect gives the DNA Genealogist an issue as it effectively screws up the inherited DNA which in turn affects the data Tools used by us.

Cousins marrying is called Pedigree Collapse and if you find that it has happened once it is very possible that it has happened more times, especially with small isolated rural communities or those of the religious or ethic minorities within a specific region.

[brigidmac]

Penelope it does sound a bit strange if the matches are high matches

Did you check that the DNA is not linked to wrong home person attached to your relatives. Father instead of himself

 that would only  explain thru line connections tho

 the  actual DNA will divide into 2 separate parents to show matches  who have code names and no trees

Do let us know if you work out what caused that 🤔

[brigidmac]

My only idea is if his mother's birthfather or a grandparent  was somehow related to his father's side of the family .

Are any of the matches connected to the maternal grandfather s family that you have on the tree

The mothers parents being 1st cousins would reduce the number of matches but make the cm.higher because she only has 6 great grandparents instead of 8..(less variety

[brigidmac]

Someone told me today that her mother was given over as a baby to the birth mothers brother + sister in law to raise

In  this case if the descendants didn't know the story all DNA matches would connect to father's side and none to the mother unless the connection was farther back .

Which made me think of your scenario . I wonder if it could be something like that .

* If the "grandmother " (fathers mother)  had a late baby that the young couple took on that would explain why seemingly paternal matches all come out as maternal .

[brigidmac]

I think the latter explanation is the most likely especially if DNA amounts are higher than average

We often consider babies being raised by grandparents but rarely the opposite scenario of a child raising their mother's offspring.

But it would come as a shock to the person if  their " mother " was actually their brothers wife and not blood related .

*Or if his " aunt " was really his mother

& His father was his uncle or brother