Early Life
Isabella was the daughter of
Donald, tenth Earl of Mar and
Elena, daughter of
Llywellyn the Great. Given that she marred in the mid 1290s, she was probably born in the 1270s; some sources suggest 1277, making her 19 when she died (see below).
Family Life
Isabella married
Robert de Brus, the future Robert I of Scotland, about 1295. They had one child,
Marjorie, in c. 1296. Marjorie subsequently married
Walter Stewart, High Steward of Scotland.
Death
Isabella died shortly after the birth of her only daughter Marjorie, in c. 1296.