Thank-you Roy for the information. I hadn't considered twins ! This could explain why my notes didn't seem to quite make sense. You asked how my search for information is progressing. I will try and briefly summarise my findings so far. I do not claim them to be either correct or complete so would welcome any comments or corrections if anyone spots something.

Firstly Robert Casement ( Of the Laxey Wheel) was my ggg grandfather through his daughter Agnes. Robert ( bp5-3-1815 Lonan) was the eldest of 7 chidren born to John Casement ( bp 11-3-1792) and Catherine White ( Peel). John was I believe bp 11-3-1732 ( Lonan) . He had 3 siblings, Jane ( bp1784) Robert ( bp 1786 ) and Margaret ( 1789) . John's parents were John ( bp 1759 , Lonan )and Jane als Kinley. John was probably one of 6 children, Betty ( 1757), John (1759), Esther (1762), Jane (1765), catherine ( 1768) and William ( 1776) , born to Robert Casement and Susannah als Burne . I am less sure of the links now. It is possible that this Roberts' parents were another Robert ( who was baptised in Lezayre and died in Lonan (1737) and Alice Garrett.( m in Lezayre in 1723). Their children were possibly, Robert (bp1725 Lez) , John (? Lez) and Esther
( Bp 1735 Lonan) , Jane ( 1738 Lonan). This would explain the movement of one line of the Casements from Lezayre to Lonan. This is as far as I have managed to get going backwards. I decided to begin earlier and try and find links the other way. I have found the Casements of the Kella and Grange, Lezayre, but have not managed to find a link either between these two families or indeed between them and Robert Casement and Alice Garrett. As the Casements of the Kella emigrated to Ireland I do think the link between the families ( if any) was before 1700. As for Robert and Alice , was Robert related to the Casements of the Grange?