there was a McAllister family on the Island that might fit - Terrence/Torens m Ann Collins (from an established Roman Catholic family in Douglas) m Malew 18280819 with two Roman Catholic bapts (ann_Jane + mary) both children appear to have died young; Ann Collins is bur age 28 at Douglas St Georges 18320725 - Terrence then appears to marry Mary Cowen at Braddan 18341214 but is himself buried Braddan 18361111 age 35 (tho with one child Mark bapt Douglas St Barnabas 18350927) ; Mary Cowan goes on to marry Philip Lewin and she + mark can be found in the 1841c census

This is derived from census Igi + transcribed cathlolic records - burial of Roman Catholics at Douglas St Georges was not unknown and RC's needed to marry in Anglican church at that time for their children to be legitimate however St Barnabas was run by a rabidly anti Catholic vicar so the later bapt is unusual.

Note that there is no Thomas but there is a gap in Terrance + Ann Collin's children that would suit - however no obv contender found in 1841c