Seeking Connections Family for John Allen and Margaret Mottow

Hi

I'm starting on my mums family tree but she doesn't remember many helpful detail.

I think I've found a couple of steps back to her great grandparents but I need corroborating evidence to be sure.

Margaret Allen (née Mirror) married to John Allen (a Baker). Lived in Monaghan.
Her daughter Elizabeth married William Millar (my grandparents) and moved to Belfast.

It looks like Margaret's father and possibly grandfather were named William Morrow.
Hoping to find out more...

Thanks,

Jo.