I agree with Frances that you must first be absolutely certain that your line is correct, generation by generation, back to this first William Taggart given in my posting which you are answering.

Once you have done this, (or if already done, can you give us an outline?), this first William mentioned also left a will.
TAGGART, William 1681-2 Mal Epis will LDS film no: 0991644.

From Manx Notebook (Frances):
"1681-2 E 374 w TAGGART William dated 14 Sep 1687;owes 29s 3d to Jo Corrin (being his mothers goods), owes £8 of their portion [?m/c] to Jo Caine + daughter his wife;2 daus as yet unmarried Isable + Jony taggart jt exexs - at age + sworn;note that money left + due to Jo Corrin is paid + acked annexed to mother's will in 1663;"

Please note "annexed to mother's will in 1663". If you can identify his mother from her will it should take you back another generation. It appears that he was her executor in that he was swearing that legacies were paid. So in any transcript or summary of her will his name should be shown.
- Or you could go through the Malew Epis wills for that year and earlier yourself, looking for William and his mother, and add to the will transcripts? (I don't see them in Joyce Oates's Arch transcripts.)

Sue