The word for 'sisters' is chwiorydd.
chwaer
her sister is Katie welsh
Mae dwy chwaer gyda hi.
'Mae gen y chi ddau chwaer'
In Irish it's "deirfiúracha" In Welsh it's "chwiorydd" In Scots Gaelic it's "peathraichean" In Manx: In Cornish: In Breton:
I know for a fact that people in Wales are called Welsh.
"You are Welsh" = Rwyt ti'n Gymreig
Draig Gymreig
'gyda dy Gymraeg di' is 'with your Welsh'
The Welsh word for "Welsh" is Cymraeg :)
No in Welsh is dim.
ymchwil Gymreig = Welsh research ymchwil Gymraeg = Welsh language research