Willem Hermanus Brink

I am desperately looking for the link between my great grandfather Willem Hermanus Brink born approx 1840. I have confirmed various facts but am unable to establish who his parents were.
He married Elsje Sophia van Zyl on 23 July 1872 in Robertson Cape Province.
His 1st child was Christina Cornelia (named after his mother in law) who later married Kok was born in Robertson om 1 May 1873, Son Willem Hermanus born in Robertson 19 March 1875, Hendrik Paul who seemed to be named after the Fick person who attended his christening born 28 August 1877, then his daughter Wilhelmina Dorethea born in Robertson on 24 September 1879, (her whereabouts can only be traced to the christening of her brother Willem's s 1st child.) Son Frederik Jacobus was named after his father in law, born in Robertson in 1880, Son Andries Jacobus was born in Robertson om 9 Jan 1883, my grandfather Johannes Jacobus Brink was born in 20 August 1885. They moved to the Freestate and settled in Clocolan, Ficksburg, Senekal area. My great grandmother died in Peka on the Basutuland border on 18 February 1902.