Heylyn was born in Burford, Oxfordshire, the son of Henry Heylyn and Elizabeth Clampard. He entered Merchant Taylors' School in March 1612.A register of the scholars admitted into Merchant Taylors' School At 14 he was sent to Hart Hall, Oxford, and matriculated from Magdalen College, Oxford, on 19 January 1616, aged 16. He was awarded BA on 17 October 1617 and was elected a Fellow in 1618.'Alumni Oxonienses, 1500-1714: Hawten-Hider', Alumni Oxonienses 1500-1714: Abannan-Kyte (1891), pp. 679–705. Date accessed: 15 January 2012 He lectured on historical geography at Magdalen.
