Translation:Mar sin leibh athair.
"Mar sin leat/leibh" means 'the same to you'. It was originally a resposne to "Beannachd leat/leibh", which means 'blessings be with you'. But lately people have just been saying 'mar sin leat/leibh' back and forth and it... sounds a bit awkward to me personally. (I'm a skye gàidhlig speaker)
A question for any of the native Gaelic speakers that read these. Would you use sibh forms with your parents? Or thu forms? Tapadh leat or tapadh leibh? I speak Spanish and while there are a few dialects of Spanish that sometimes use the formal with parents, generally tú is used within the family. Just wondering how different it is, or if it's also regional.