Complex sentence: He entered at the port of Southampton on board the "Habana" on 23 May 1937, him and his brother Luis being among 3,889 Basque children fleeing the Spanish Civil War.
Split into simpler sentences: He entered at the port of Southampton on board the "Habana" on 23 May 1937. Lezama and his brother, Luis, were among 3,889 Basque children fleeing the Spanish Civil War.