I have sent you a message on gr and opened up my tree for you.
Now lets get down to the nitty gritty.
I will start with the Baines side.
We know from the marriage that Sarah Baines father was Isaac.
I have now found Isaac Fullwood and Sarah in the 1881 census, and living with them as Isaac's mother-law (Sarah's mother) is Winifred Baines. Quite an unusual christian name that early. Her age is 82. So that gives Sarah's parents potentially as Isaac Baines and Winifred.
In the 1861 census, Isaac Baines and Winifred are living two doors away from Isaac Fullwood and Sarah in Sedgley !!
That marriage turns out to be Isaac Banes and Winifred Guest at Sedgley on 1st November 1819.
Their children are as follows - All baptised Sedgley.
Sarah (in the name of Bannis 7th March, 1821)
Maria ( in the name Banes 6th June 1824)
Joseph (in the name Bains 9th April 1827)
Isaiah (in the name of Bains baptised 19th January 1829 and
buried 25th January 1829)
Hannah (in the name of Banes baptised 29th September, 1830
and buried 28th October, 1830)
Twins Ann and Mary (in the name of Banes 22nd September 1836
Louisa (in the name of Banes baptised 27th November, 1839
and buried 12th December, 1839)
Looks like Sarah Baines is the eldest child.
Now to the Fullwood side (or whatever spelling was used for them also !!)
18th December 1774 baptised at Sedgley Bernard Fulwood
7th August 1797 marriage at Kingswinford Barnet Fullard/Leah
23rd October 1814 baptised at Sedgley Isaac son of Bernard
and Lea Fullwood.
Hope all these ramblings make sense to you.
Just to say that nothing is 100% sure, but I am a bit of a stickler for accuracy as far as you can get it.
I can tell you that if this was my FH, I would be happy with the above.
Let me know what you think.