Please HELP with our FAMILY TREE CONNUNDRUM of the PLANT TREE

[Ruskie]

And a possibility for Lydia:
Lydia Malkin bapt 4 Sept 1757 St John the Baptist, Burslem
father: John.
mother: Jemima

It is curious that they married in St Peter Ad Vincula in Stoke if these are the same people. It seems that Lydia may have been under age, which may explain it. Or she was pregnant with John - as those dates look pretty close. 

All just speculation. Further research and confirmation required. 

[Annette7]

As William and Thirza named one of their sons Ralph, and 1841 census show Thirza bc.1790, I would say that Thirza is indeed the sister of your Ralph Plant:

Ralph Cook bp.1/4/1816 St. Johns, Burslem son of William and Thirza (on familysearch).

Annette

[Ruskie]

There are a few Plant families in a similar area, but not too many to be unmanagable. 
I think if you spent a bit of time you could easily put them into family groups using the information available on Freereg alone.
Agree with Annette. It is all pointing towards your Ralph and Thirza being siblings. Also, she seems to be the only Thirza around.

[glenton]

Many Many Thanks to Ruskie  and Annette  for replying to my message - I  could not find another Thirza Plant other than the one I had researched. Great !!
        Glenys