Complex sentence: The princess and her brother, Wilhelm, were the only grandchildren born in their grandfather Prince Albert's lifetime; the young couple brought Wilhelm and Charlotte on a visit to England in June 1861, six months before Albert's death.
Split into simpler sentences: The princess and her brother, Wilhelm, were the only grandchildren born in their grandfather Prince Albert's lifetime. Victoria and Frederick in turn brought Wilhelm and Charlotte on a visit to England in June 1861, six months before Albert's death.