Hi
Unfortunately - there are too many Ethel Bottomley entries on the 1901 census which may be her so you would need to buy a copy of that 1912 marriage cert to find her age and her fathers name to be able to pinpoint the right one
The reference is March quarter 1912 Halifax Volume 9a Page 704 and you can order online at
www.gro.gov.uk/gro/content/certificates/The cost is £9.25 GBP
You will already know from the birthyears that all of Clements siblings will now be deceased so you are dependant on finding their children/grandchildren.
His brother Milton died in 1957 in Halifax
Like your mum - any descendants who may be living will be quite elderly and it is against Rootschat policy for us to post details of any person who could still be alive
Any info we find that may help you to contact living relatives will have to be conveyed via the pm system
I would strongly recommend you check the Genes Reunited entry found by Crisane as that may sort a lot of info for you