Thanks Heywood
Just seen post 109 .. thanks for that :-)
Mum always thought they were Platt but it now appears they were Thomas (as the birth certificates). Think mum just assumed that as she was told they were full brothers that they were Platt as well.
I have spoken to dad about his visit to Bolton with mum to tell Percy s brother he had died. Dad said it was John. Doris's name is mums recollection ... dad has no idea!
So I think John Thomas married Doris but can't find a record.
Mum said the other brother was insane. She said he thew himself in front of a train ... but that again may be totally wrong. I know this happened to an uncle on her side ( we have a lot of insanity in our family) and wonder if she was confused. Cant find anything on him either.
If I could just find Margaret in 1891 I could see if she was a domestic servant but she is a mystery ... can't even see her birth in Chorley. There is a Margaret Ann Platt in Preston but that's not her :-(
I gave searched for Margaret over the days with no joy.
She may have stayed with John.
She may have left him and reverted to the Platt name.
She may have gone to live with someone else!
A while ago, you were looking at a John Platt / Doris marriage?
Was Percy's brother definitely a Platt? I can't see anything definite for the Thomas boys. 
I also saw the one in Winwick but the occupation is questionable.