Hi Liz,
The Phillip Lilbourne that you refer to, was Mary Lilbourne's brother. He was born C1711 in Rye. Their parents were Phillip Lilbourne b. 14th Sep. 1680, Rye and Mary Graves. Phillip b.1680, had a sister Elizabeth b. 6th Nov. 1676, who married Richard Vousdon and it was their daughter Mary who married John Clark. So yes, they do belong to the same family. Siblings Mary and Phillip Lilbourne were Mary Vousdon's cousins.
Viv.