Maughold parish register has:
16 Sep 1875
Thomas CHRISTIAN, 24, Bachelor, Carter, King St, Ramsey [father] William Christian, Carter
Margaret Jane KENNAUGH, 23, Spinster, Ballure Rd, Ramsey [father] Casar Kennaugh, Labourer.
Sister's marriage:
1 Dec 1877
John JOUGHIN, Full age, Bachelor, Porter, College St, Ramsey [father] James Joughin, Stone Mason
Elizabeth KENNAUGH, Full age, Spinster, Lezayre, [father] Caesar Kennaugh, Labourer.
Her brother's marriage:
19 Feb 1870
John Caesar KENNAUGH, Full age, Bachelor, Servant, Andreas [father] Caesar Kennaugh, Manservant
Catharine COMISH, Full age, Spinster, Maughold, [father] John Comish, Miner.
John Caesar Kennaugh was bapt 27 Jan. 1849 in Andreas, the son of Caesar K & Margt Kinrade. There is a burial for KENNAUGH, Caesar aged 86 Andreas 17 Oct 1873 on Brian Lawson's index.
I assume that this is Thomas Christian's bapt: 6 Sept 1849, Maughold, son of William Christian & Eliza COWN.
William Christian & Elizabeth Cowin were married Maughold 9 Jul 1839.
William a widower, Elizabeth by consent of her father. [So she was under the age of 21.]
There was "Jumetta Eliza dau of William Cown & Ann Looney privately bapt 17 Aug 1819" Maughold, which could have been her. - I can't see another possibility in Maughold bapts.
Other children of William Christian & Eliza Cown bapt Maughold:
Eliza 24 Jan 1841
Elizabeth 1 Jan 1843
Ann 2 Mar 1845
Margaret 15 Aug 1847 [to 1848 only, but others are on the IGI].
1841 Maughold census:
1 2 4 Lewaigue William CHRISTIAN 32 Ag lab Isle of Man
1 2 4 Lewaigue Eliza CHRISTIAN 21 Isle of Man
1 2 4 Lewaigue Eliza CHRISTIAN 3mo Isle of Man
1861 Maughold census:
2 2 Folieu Farm William CHRISTIAN Head MAR 52 Farming 70 acres, b. Lonan
2 2 Folieu Farm Elisa CHRISTIAN Wife MAR 41 b. Maughold
2 2 Folieu Farm Betsy CHRISTIAN Daughter UNM 18 b. Maughold
2 2 Folieu Farm Ann CHRISTIAN Daughter UNM 14 Maughold
2 2 Folieu Farm Thomas CHRISTIAN Son UNM 11 Maughold
2 2 Folieu Farm William CHRISTIAN Son UNM 8 Maughold
2 2 Folieu Farm John R CHRISTIAN Son UNM 6 Maughold
2 2 Folieu Farm Robert CHRISTIAN Son UNM 3 Maughold
This says that William Christian was born Lonan, not Maughold. This would be worth double-checking in other censuses.
Sue