Good evening Frances,
I am a member of the IOMFHS and have been researching my Manx heritage on and off (more off than on it must be said) for several decades. I was originally going to pose this question to Nigel Crowe, the font of all knowledge on this subject, but alas he passed away last year. I have copies of Liber Assed back to 1626 and Liber Vast to 1630, but understanding the content hiding in the scribble is beyond me other than the numerals where the dots show me where the rent is.
To date my research has taken me back to John Kewley Jnr of Ballanard, so you see I'm in striking distance of Gibbon Mac Kewley but can't quite get there. What I have is the following, in reverse order:
Gibbon Mac Kewley of Ballanard in the house of Keys in 1502
John Kewley, "the first recorded Manorial Tenant of Ballanard" in 1507
Mark Mac Kewley and Michael Mac Kewley of Ballanard in 1511
The next definite point is the burial at Old Kirk Braddan of John Kewley Snr on 15 January 1627, leaving his son John Jnr and his mother Ellin nee Corkill - however it is uncertain whether John Jnr was now the land holder and liable to pay the rent to the Lord of Man. Liber Vast records the event thus: "A Jo Kewley, son of Tho's, bur Braddan 15/1". inferring, I think, that John Jnr was the heir to Ballanard. To have inherited land holdings John Kewley Jnr must have been at least 21 years of age ie, born in or before 1606, also to have married and sired a son John Snr must have been born around 1590 or earlier and Thomas, as the father of John Snr would have been born around 1570 or earlier.
However, this doesn't seem to agree with what you have.
Just to add to the picture, back in 1626 Liber Assed stated that John Kewley Snr also held Glencruchery and Ballamanaugh Quarterlands as well, so John Jnr would heve inherited quite a lot of land.
And there again i may be misinterpreting the meaning of what is being recorded. I am just trying to bridge the gap between Thomas and the Mark & Michael Mac Kewley in 1511 and Gibbon in 1502.
Any advice will be gratefully received.