Jaydn Denly made his Kent first-class debut as Essex dominated day one of the County Championship Division 1 match between the sides at Chelmsford on Friday.
Denly, 18, was a late call-up after fellow all-rounder Joey Evison struggled with a tight calf in the warm-ups - but then spent the day toiling away in the field.
Denly played alongside his uncle Joe Denly. It was the first time an uncle and nephew had played in the same Kent side since 1854.
Dean Elgar hit the 49th three-figure score of his first-class career and Matt Critchley chipped in with the eighth century of his career, as county cricket resumed its trial of the Kookaburra ball in first-class cricket.
Former South Africa captain Elgar put on 89 for the fourth wicket with Critchley, who in turn shared stands of 58 with Paul Walter and 80 with Michael Pepper.
When Elgar was out after almost four hours at the crease, chipping Matt Parkinson (2-110) tamely to short square leg, he dropped his bat and kicked the ground in frustration.
But, by the close, Essex had built on the foundations he had laid to reach 421-6 with Critchley still there on 103 from 173 balls.
Earlier, the home side had lost two wickets in the first four overs.
Feroze Khushi went first ball, beaten by one from Australian overseas bowler Wes Agar (1-85) that he decided to leave which took out his off-stump. Tom Westley drove loosely at George Garrett (2-64) and was caught behind by Harry Finch.
But Essex recovered from 10-2 to 169-3, former Kent wicketkeeper-batsman Jordan Cox (67) also contributing well before he was lbw to Garrett.
Critchley then came into the middle and reached his 50 when he creamed Jack Leaning (0-48) through the covers to the fence.
Critchley and Paul Walter chalked up the third half-century partnership. Walter brought up Essex’s 300 with the type of straight six off Leaning that has characterised his career.
A second soon followed before Walter chased another gift from Parkinson but only succeeded in picking out the long-off boundary fielder.
That ushered in Michael Pepper who clicked immediately into white-ball mode in scoring 49 from just 42 balls, including seven fours and a six lofted through the covers off Leaning. He departed when upper-cutting Nathan Gilchrist (1-83) to deep third man.
As the light started to deteriorate in the early evening, Critchley reached his ton from 168 balls - 20 slower than Elgar’s and with just four boundaries and a six.
South African Simon Harmer was also unbeaten on 12 at the close.
