McGinn family from County Down

My McGinns left Ireland about 1820, well before the famine years.

I do not know a parish or town

land and no personal family history has survived. 

The only reason I suspect Down is a grave marker of Henry, one of three boys who emigrated. They settled in Matilda Tp., Dundas County in now Eastern Ontario.

Fatherr unknown

Mother, Margaret ???????

Son Daniel 1803-1828, my gggf.

Daughter Rosanna

Daughter Eliza

Son John Alexander

Son Henry

Son Patrick

All surname McGinn.

The family was Roman Catholic but Daniel, my gggf married in an Anglican Church so we have an RC side and a Protestant side!

The father might have been Daniel or John ?