I don't know if you wanted help tracing the children of Wilfred and Martha forward (as far as we can, when it gets to living people we will not be able to post details), or if you were happy to follow it up yourselves.
Here are some steps - just ignore if you have already done this yourselves.
Looking at the list I gave of "possibles" for the 15 children of Wilfred and Martha
1) Clement. He can ruled out as can be seen on censuses with parents George and Sarah
2) Kate, Fred and Emily -- likewise. They are all children of Geroge and Sarah and can be seen with them on 1881 census
3)So, John Wilfred bn 1884 seems to be the first child of Wilfred and MArtha. He was christened7th Sept 1884 in Mexborough. He can be seen on 1891 and 1901 census with Wilfred and Martha in Swinton, giving place of birth as Swinton. By 1911 he has a wife Ada and some children.
Marriage Jul/Aug/Sep 1906 Rotherham
John Wilfred Harrison and Ada Petty.
Looks like he died in WW1, and Ada remarried:
https://www.findagrave.com/memorial/107095054Harrison children with mmn Petty, in Rotherham Reg District:
Oct/Nov/Dec 1906 - unamed male, mmn Petty
Oct/Nov/Dec 1907 - Mary Mason Harrison mmn Petty
Apr/May/Jun 1909 - Wilfred
Jan/Feb/Mar 1911 - Rose Ellen
Ap/May/Jun 1913 - Florence
Jan/Feb/Mar 1915 - Harriet Ann
They are listed on John Wilfred's WW1 record too.
That gives a few more to follow up, if you havent already.