Complex sentence: He was married to Anna Maria Lastrop (1723--1761) and had two children, but after his son Rudolf died in Suriname in 1768, aged 20, his daughter Elisabeth Berenberg remained as the only heir and last surviving member of the Berenberg family.
Split into simpler sentences: He was married to Anna Maria Lastrop (1723--1761) and had two children. Hence Johann Berenberg's daughter Elisabeth Berenberg remained as the only heir and last surviving member of the Berenberg family.