I had a look at this line a while back, and the information I gathered was:

Thomas Cowin (born c1777) possibly baptised 1st October 1781 (but I'm not sure).
He married Jane Christian at Andreas on 7th June 1803.
1841 Census: Aged 60 (approx) at Langahan
Sons: Thomas and Robert (both in 15-30 age group) Daughters Jane (30-35) and Elizabeth(20-25)
1851 Census: Aged 74 at Laugaghyn
living with brother James (61) and nephew Thomas (10).
Died: 1854?
Also had a son Daniel born c1808.
Bap. 9th Oct 1808 at Onchan.
Daniel married Mary Cleator (born 1808 in Jurby) in 1838.