Mundell family in Co. Derry

I am seeking Irish relatives of my family from Co. Derry and Co. Antrim; my family name is Mundell, and I know that I have living relatives there still.  I am trying to research connections to those, hopefully still living, come from my family line.  Any help or hints are greatly appreciated.

I can trace my Irish-Canadian family (with documentation) back to William Mundell (b.1787 d. approx 1840) & his wife Susanna (nee GIlmour, b. 1784 d. ?) from Co. Derry.  William was killed by a run-away turf cart; his wife Susanna took their 6 children and followed Wiiliam's brother John Mundell (and his wife Ann (nee Hipson) when they emigrated to Canada some time before 1845. The eldest son of William & Susanna was my 3rd great grandfather Joseph Mundell (b 21 Feb 1807) who I have documentation was born in Derry (see photo of is tombstone in Washburn, Ontario, Canada, attached).  I have documentation from the 1861 Census of Canada that Susanna Mundell (Gilmour) was still alive and living with her eldest daughter Margaret and her husband John Ketchem (who was born in Scotland).  The census shows she was a widow, consistent with the story handed down over the generations.  

I know the family were Protestants as they identify as Presbyterians in the 1861 Cencus of Canada, likely Scots-Irish - but I'm not certain.  It is at this link - Joseph Mundell (and his parents Susanna & William) that I get stuck.  Can anyone help me?

Thank you

Grant Mundell

grantmundell@gmail.com