Some people have the Thomas Markenfield who m. Alianor/Eleanor Conyers as father of Elizabeth, but J.C.B. Sharp states that the pedigree is as I have it. The death dates of Thomas & Eleanor would support Mr. Sharp. The Thomas who m. Eleanor Conyers lived until 1497 (according to Sharp & also to Faris' Plantagenet Ancestry) and Eleanor Conyers lived until 1493 (same sources), while Elizabeth (whose marriage arrangements were made by 1416) was born, say 1410 or earlier with her parents born in the 1390s or earlier, which makes it extremely unlikely that they would be parents of Elizabeth (both would have lived to be 100 or more).
The following is the portion of the pedigree showing the descent from Thomas & Beatrice (including Elizabeth mentioned as sister of Sir John) contained in a post to SGM, 5 May 2000, by J.C.B. Sharp:
From: J.C.B.Sharp (jcbs@@obtfc.win-uk.net)
Subject: Markenfield
Newsgroups: soc.genealogy.medieval
Date: 2000/05/05
12. Sir Thomas, pardon for murder 1394 (Cal Pat 1391-6 469), living 1415, m Beatrice Soutill.
13. Sir John, in France with Richard earl of Salisbury 1431, will 1448 (SS liii 124n), m1 Joan Midelton, m2 a Hastings, m3 Margaret d/o Sir John de Midelton, his brothers Thomas, Robert and Peter all dsp, his sisters were Joan the wife of Sir Roger Ward, Elizabeth wife of Walter Calverley and Isabel wife of John Mauliverer of Allerton.
14. John, m. Margaret d/o John Hopton of Swillington, his sister Margaret m. John Midelton.
15. Sir Thomas, steward of Ripon and Kirkby Malzeard, died 1 May 1497 (YASRS xxxiv 213), will (SS liii 124-6), m. Eleanor died 5 June 1493 d/o Sir John Conyers, his brothers were John, William & Robert and his sisters Joan & Ann the wife of Christopher Conyers of Sockburn.
16. Sir Ninian, knighted at Flodden 1513, will 1528 (SS lxxix 232-5), m1 Dorothy d/o Sir William Gascoigne, m2 1526 Eleanor d/o Henry lord Clifford, his elder brothers Thomas and Christopher died young.
17. Thomas, died 1550, m Margaret d/o John Norton, his sisters were Alice wife of Robert Malliverer of Woodersome and Eleanor wife of Robert Aske.
18. Thomas, implicated in the rebellion of 1569, forfeited and died in Spain, m Isabel d/o William Ingleby of Ripley, he had brothers William & John and a sister Anne.
J.C.B.Sharp
London