Here is some more information that you may not have.
Agnes de Erth and Sir Edward Bruce also had two other children, one a male son whose name I don't know and was born after 1395 and another son, William, who died in 1485.
I also have info that the castle was handed down through Robert's line.
Agnes de Erth had two sisters, one full sister by the name of Elizabeth.Their mother's name is unknown.Agnes also had a half sister, Mariota or Marjory, whose mother's name is unknown.They may actually all have the same mother because I have only seen it once that there were two different mothers.
I have also seen where Agnes de Erth was married another time to a male Elphinstone and they had a son, John.
This information was all obtained before I really got into studying my line and unfortunately I did not document the sources.
I wish I could link my Airth's to the ones in the castle.I am so close, only about 300 years, and everywhere I lead seems to end in a brick wall.If you have any other info that may connect me, I would really appreciate hearing from you.