Your list of siblings for Robert caught my eye. Archibald McBROOM (1791 Kirkoswald -1860 St. Quivox)married 1820 to Helen ROBERTSON. Children that I have include: John (1821), James (1822), Elizabeth (1824), Sarah (1836), Gilbert (1838), Hugh (1839), William (1841) and Margaret (1843). There were at least 4 other children. Archibald was the s/o Gilbert McBROOM and Elizabeth THOMPSON. I have determined that John and Margaret imigrated to the USA -- Margaret probably abt 1860-1865, John probably earlier. They settled initially near Pittsburgh, PA in Chartiers Twp. Most of the children were born in St Quivox, Ayrshire; Sarah was born in Kilmarnock, Ayrshire.
Does any of this information match up with your family information?