Their daughter, Margaret, is said to have married Bernard Kearney, who is said to have been the son of my great-great-great grandfather Bernard (a.k.a. Barney) Kearney (also spelled "Carney" sometimes, back then), and had one daughter, Elizabeth Kearney, born February 17th 1869.
John Tynan and his wife are both buried in Sturgeon, PEI. I have the dates of their deaths.
There seems to be a bit of a mystery, as my g-g-g grandfather, in his will dated Jan. 9th 1867 (the day he died) leaves some animals to "my granddaughter Margaret Tynan, upon her marriage ..."
I'd be happy to discuss and exchange any info you have.