Hi Sandra.
I can help because I'm descended from Bahee CHRISTIAN, the eldest child of Thomas CHRISTIAN and Ann COWN/COWIN. Bahee married David GELLING, so they are my 4xgr-grandparents. Thomas & Ann married 15 May 1739 in Onchan and Bahee was baptized in August of the same year.
According to their Lonan wills or admins (Ann in 1765 and Thomas in 1766, both on Brian Lawson's will site) they had 7 children, the males being Thomas, William and Patrick, and the females being Bahee, Mary, Elizabeth and Ann. Bahee isn't mentioned in her mother's will, but she has a Bridget instead which I'm assuming is the same as Bahee.
Onchan baptisms are very annoying because they don't list the mother's name during the mid 1700's when all these folks were baptized. However, the two wills above plus the one from Margaret Christian als Callow, which I'd never seen before (thank you Brian!) really help to sort them out.
These ones belong to Thomas CHRISTIAN & Ann COWIN md 15 May 1739 Onchan
1. Bahee bp 14 Aug 1739 Onchan, m (1) David GELLING 9 Jul 1765 Lonan, m (2) William CURPHY abt 1780, bd 10 Feb 1803 Lonan.
2. Mary bp 3 Feb 1741/2 Onchan, m Philip STOLE 8 Feb 1766 Lonan, bd 10 Apr 1808 Lonan.
3. Elizabeth bp 21 Nov 1744 Onchan
4. Thomas bp 25 Dec 1745 Onchan. Sworn supervisor of younger brothers William & Patrick in father's 1766 admin.
5. Ann bp 7 May 1752 Onchan
6. William. The baptism 18 May 1758 Onchan could be him, or the other William below.
7. Patrick bp 3 Apr 1761 Lonan
These belong to Thomas CHRISTIAN & Margaret CALLOW md 16 Oct 1742 Maughold
1. Jane bp 24 Dec 1743 Onchan, md William LAWSON 14 Oct 1768 Braddan.
2. Thomas bp 25 Dec 1745 Onchan
3. Margaret bp 30 Jan 1747/8 Onchan, md Thomas HAMPTON 13 May 1773 Onchan
4. John bp 25 Jan 1749/50 Onchan
5. Ellinor bp ca 1752, md Thomas WHEELER date n/k
6. Joney bp ca 1755
7. William bp ca 1758. Bapt for Wm in other family above may be him.
8. Matthias perhaps bp 6 Jan 1761. IGI says "Thomas Christian & Mary Christian" so this might be a different person. Date is 2 months before Margaret's death.
As for parents of these Thomas's, my candidate for the parents of "my" Thomas is bp 28 Sep 1707 Onchan s of Thomas Christian of Ballakilmartin Onchan likely by Bahee COTTIER with whom he was having an affair at the time. His father John Christian in his 1707 will stated son Thomas was to be disinherited if he married Bahee COTTIER. Instead, he married Margaret SKILLICORN in 1708 and had 5 children with her (there also is a John bp 1705 who I'm also assuming belongs to Bahee). Bahee married Robert FARGHER in 1709 and I found 6 children on the IGI. Old Thomas Christian of Ballakilmartin died in 1771 age 90 and outlived his son Thomas. His parents were John Christian (d 1707) and Catherine COWN (d 1721)
At this point, I don't know who the other Thomas's parents would be.