The 27-year-old man was on board a ferry from Spain’s north African enclave of Melilla to the mainland Spanish city of Almeria.
The surviving brother, who has a French passport, has since been charged with involuntary manslaughter.
On Sunday, four migrants died trying to swim to another Spanish enclave.
The men, from sub-Saharan Africa, were attempting to swim around a fence from Morocco to the enclave of Ceuta.
Another three were rescued, Morocco’s interior ministry said.
In May, an eight-year-old boy from Ivory Coast was discovered inside a suitcase as it passed through a security check point in Ceuta.
He was later reunited with his mother, who lives legally in Spain, after he was granted a temporary residence permit.
Human Rights Watch says at least 4,300 people entered Ceuta and Melilla illegally in 2013, compared to 2,804 the year before.
In February last year, hundreds of migrants stormed the fence in Melilla in one day, with around 100 managing to make it into the enclave.