Greetings Mark,
Unfortunately I have no idea who Lucy Sinnock's parents or siblings are. All I know about her is her marriage and her children.
The Sinnocks I found in Bexhill:
FHL film 1364151.. transcripts of PRs and Bts. Bexhill
Baptisms:
Mary dau William SINNOCK 12 Nov 1693
William son William & Mary SINNOCK 6 Dec 1696
Langford Richard son " " " 26 May 1700
Nicholas " " 4 Nov 1705
(sp SIMNORK)
John son Richard and Mary SINNOCK 24 Aug 1694
Richard " " " 25 Jan 1695
Thomas " " 24 Jan 1696
Elizabeth " " " 17 Feb 1701
Elias " " " 28 Mar 1708
Richard " " " 20 Sept 1713
Thomas son Nicholas and Sarah SINNOCK 12 Sept 1734
William " " " " 3 Aug 1736
Nicholas " " " " 15 Sept 1738
Mercy dau " " " 9 June 1740
Elizabeth " " " " 26 Sept 1742
Thomas son " " " 11 Dec 1743
MARR:
Thomas SINNOCK and Elizabeth SINDEN 4 May 1727 Lic
BURIALS:
Richard SINNOCK son of Richard and Mary 4 Feb 1695
An unbaptized son William and Mary SINNOCK 20 Nov 1695
William son William n Mary SINNOCK 18 Apr 1706
John " " " " 24 Dec 1714
Mary dau William n Mary SINNOCK of Castle Parish Hastings
16 June 1713
Mary wife of Richard SINNOCK 7 Sept 1715
Mary wife of William SINNOCK of Hollington 15 Mar 1726
Elizabeth dau Nicholas n Sarah SINNOCK 7 Oct 1742
Thomas son " " " 13 Dec 1742
widow SINNOCK 8 Sep 1776
Nicholas SINNOCK 28 Feb 1777
Thos SINNOCK 29 Sep 1788
William SINNOCK 15 Oct 1792
Regards
Kaye