They're separate families, I believe, both Thomas and Sarahs had other children in their respective areas.
Here's the marriage for the Braintree Thomas Hedges:
THOMAS HEDGES
Male
Event(s):
Birth:
Christening:
Death:
Burial:
Marriages:
Spouse: SARAH RAYNER
Marriage:
14 NOV 1816 Braintree, Essex, England
Children:
1. Thomas Hedges, chr. 23 Aug. 1822, Braintree
2. Mary Maria Hedges, chr. 23 Aug. 1822, Braintree
3. William Hedges, chr. 24 Jul. 1824, Braintree
4. Emily Hedges, chr. 6 Jul. 1827, Braintree
5. Sarah Hedges, chr. 6 Mar. 1829, Braintree
6. Joseph Hedges, chr. 15 Jul. 1831, Braintree
7. Edward Hedges, chr. 2 Oct. 1833, Braintree
8. Charles Henry Hedges, chr. 9 Mar. 1836, Braintree
Note: Thomas and Mary Maria were christened together, so both of them could indeed be born before 1822, especially as the couple married in 1816.