Complex sentence: In 1843 Henry Hucks Gibbs (later Lord Aldenham) nephew of William joined the business in which he became more and more involved and when William retired, he left Henry in charge.
Split into simpler sentences: In 1843 Henry Hucks Gibbs (later Lord Aldenham) nephew of William joined the business in which he became more and more involved. When William retired, he left Henry in charge.