Here is the marriage of Isaac Siggers/Seggars and Elizabeth Warner in Mistley and their children.
From:
https://essexandsuffolksurnames.co.uk/parish-register-transcriptions/essex/mistley-st-mary/SEGGARS Isaac bachelor WARNER Elizabeth spinster 22 Jan 1794 By banns.
They all sign except the bride. Witnesses: John Gaymer, Elizabeth Lamberd
Child / gender / father / mother / date
SEAGERS Elizabeth F Isaac Elizabeth 12 Apr 1795
SEAGARS Isaac M Isaac Elizabeth 15 Apr 1798
SEAGGERS Mary Ann F Isaac Elizabeth 23 Nov 1800
SEAGGERS Sarah F Isaac Elizabeth 05 Dec 1802
SEGGERS Eliza F Isaac Elizabeth 20 Oct 1805
SEGGARS Isaac M Isaac Elizabeth 13 Dec 1807
SEGGARS John M Isaac Elizabeth 20 May 1810
Also, have a look at the parish registers of Tendring. This is about five miles from Mistley.
Tendring
https://essexandsuffolksurnames.co.uk/parish-register-transcriptions/essex/tendring-st-edmund/1739 Isaac Seggers, son of Isaac and Martha
(marriage of Isaac Seggers and Martha Dardy in 1739)
1770 Isaac Segger, son of Isaac and Mary
(marriage of Isaac Seggers and Mary Snell in 1760)