There are a couple of Beckett links with my Gilbert family of Aghagallon (not far from Ballinderry).
In Aghalee on the 3rd Feb 1847, my 1st cousin 4x removed, William Gilbert married Mary Beckett, daughter of Matthew Beckett.
A couple of years earlier, in 1845, William Gilbert's sister Jane married Samuel Turtle, son of John Turtle.
This is from my notes on John Gilbert, father of the above William and Jane:
One of John Gilbert's children married a Turtle and another a Beckett. CEB Brett's book, "Buildings of County Antrim" features Laurel Hill in Aghalee. This house was owned by the Turtle family while the farm next door was owned by the Becketts. On the 14th December 1890, Isaac Cousins Turtle of Laurel Hill, only son of the late William John Turtle died, aged 38. In his will Isaac directed that all his land that he be "possessed of or entitled to whether leasehold [or] freehold and chattles to be sold and the proceeds to be divided equally between [his] two unmarried sisters Mary Letitia and Harriet Turtle." In 1891 Laurel Hill was bought by James Quinn who moved in with his wife (Jane Graham) and children. On the 23rd September 1931 James Quinn's son William married his neighbour Annie Elizabeth Beckett. As a result of this union the two farms were combined. These Turtles and Becketts were presumably related to the spouses of John Gilbert's children.
Other marriages:
On the 18th March 1880, Samuel Beckett of Aghalee married Mary Elizabeth Turtle, eldest daughter of William Turtle of Ballinderry.
There was also a Beckett-Gilbert marriage in 1978, but that's a bit recent to talk about here.