Hi,
I am a great great........granddaughter of Alexander through Robert Allan. I and other researcher believe he was the son of John & Isabel Allan, born at Newhaven, not Alexander and Helen Kirkwood. We are unable to find his death but he was shown as dead on his wife, daughter and sons death certificate in 1849. The Alexander born in Kingbarnes was still alive in the 1851 census.
Given Robert was not baptised I thought this may have been because his father had died around that time (1832). If he died at sea we may never know especially if was on whalers. Let me know if you are interested in catching up.