Daughters of George PURCELL of Castletown, Cork.

I'd like some confirmation on this family.

I have a Susan PURCELL (1804-1864) whose father is a George PURCELL born about 1765 and married Mary DELANY. Susan married my Robert Crofts BULLEN and one of their children was Rogerson Cotter BULLEN.

Mary Susannah PURCELL who I've just found whose father is also a George, this Mary married Joseph Rogerson COTTER.

These two ladies would have to be sisters???

Can anyone confirm this one for me, because I haven't found any other siblings for Mary?

Thanks,
Kellie