Complex sentence: De Vere was educated at Friesland in the Netherlands after his father was mortally wounded at the siege of Maastricht in 1632, when de Vere was only six years old; years later he joined the English Regiment of Foot serving on the continent with the Dutch.
Split into simpler sentences: De Vere was educated at Friesland, Netherlands, after his father was mortally wounded at the siege of Maastricht in 1632. He was only six years old; years later he joined the English Regiment of Foot serving on the continent with the Dutch.