Robert Robertson of Perthshire

I am researching the descendents and the ancestors of Robert Robertson. I am not certain of his birth but I'm of the opinion it was in 1798, 1799, or 1800 in Perthshire. Robert appears in the 1841 Scottish census, living on the Edradynate Estate, at Drumchanachan, with his wife Helen, four children: Jean (Jane), born in 1833, in Dull, Newton Derculich; James born in 1835, Logierait, Drumchanachan; David, born in 1837, Drumchanachan; Ellen (Helen), born in 1841, Drumchanachan. (Dull and Logierait are parishes. Newton Derculich and Drumchanachan are the homes the family lived in.) Also listed in the census was one servant. I have recently learned that the servant was named Uphimea Robertson, aged about 13. Was she related to Helen or Robert? Was she at Drumchanachan because Helen was ill?