Sue has sent me some early Looney Maughold records, and in there I found a marriage of Robert Cannan & Katr Lowny 23 May 1685. This isn't on the IGI.

Known children of Robert Looney [and presumably Joney Callow, md 25 Nov 1648 Maughold, bd 2 Feb 1676 and a 1676/77 will, not seen and not on the MNB as of yet]
1. Kat 9 Jan 1655
2. Willm 28 Oct 1660
3. Tho 14 Aug 1666

I've been studying Averil's transcription of Thomas Looney's 1692 Maughold will. I'll put here a fairly comprehensive summary:

Will: LOWNY, Thomas 1692-2 Maughold A w 0106206 (transcribed on Ian Radcliffe's site Mannincloud )
Maughall March the 20th 1691
LWT Tho: Loony who departed this life at time abovesd
Bequeathed to his Fathr & Brother-in-Law Robrtt. Canon 11s4p of wages which was due to him from Robrt. Callow Junr.
A sheep & yearling to An: Canon.
Halfe a sheep to Margrett daughtr. to the above Robrtt.
Halfe a sheep to Jony Kerroush.
A goat & 6d Legasy to his Bro. Will. Loony
A new wasquot & quoat to the sd. Robrt. and constituted his sd Fathr & Brothr in Law Robrtt Canon sole Executors of all the rest of his goods wt. soevr.
Testes: ... Kermeen & ...argrett Corteene
Exrs. sworne
Inventory included in this & ye mothers will on Record. Pledges Robt. Kerruish & Jo: [Ker = meene]
[end of will]

Some conclusions:
1. Almost certainly this will is Robert Looney's son Thomas. Robert lived to 1699. The bro-in-law Robert Cannon is Thomas's elder sister Kathrine's husband, and she likely is still alive in 1699 (Robert Cannon's will mentions wife, 4 ch Ann, Margrett, Isabel & Ellin.)
2. IGI has 3 baptisms for children of Robt Cannon: Ann 1686, Isabel 1691, Elinor 1695. Margret likely fits ca 1688.
3. Thos's will mentions Margt, d/o Robt Cannon.
4. The will mentions an Ann Cannon. This could be Robt Cannon's eldest daughter. But maybe it's somebody else, such as the Ann Cannan als Lowny buried Feb 14 1717/18. Could she be a sister? Her will mentions her [cosin] Catrin Looneys daughter, which might be relevant. For sure in 1718, Margaret Cannon was alive, Ann Costean als Cannon was dead 1708, and the younger two are unknown.
5. Ann Costen als Cannon's will 1708 has only child Margt Costen [an infant] as sole admin, husband [Ewan Costen] and 2 supervisors Aunts Margrett and Isabell Cannon. Later it says "Nov 18 1721 Aunt Margt is drawn" [ie, dead].
6. Ann Cannon als Looney's 1718 will includes sons John & Edward (both abroad) and has son Philip Cannon exec'r. There's a 1718 will for a Philip Cannon and a 1719 will for an Edward Cannon, not on MNB, which might tell us something.

And some questions:
1. Who is Jony Kerroush in Thomas Looney's 1692 will?
2. Is there a connection between Ann Cannon als Looney d 1717/18 and Thomas Looney?
3. Could the marriage of Richard Kermod to Catherin Looney 10 Jun 1701 be the widow of Robert Cannon? The timing is good, and women's surnames at that period often were their original surname. If so, it puts a damper of Averil's suggestion that this Catherine Looney is the one bapt 21 Oct 1684 d/o John Looney & Margery Woods (if Averil is right, Cath is only 17 yo.).