Sofia is the daughter of Alejandro, who is the brother of Maria. This means Sofia is Maria's niece. Since Roberto is Maria's son, Sofia would be his first cousin because their parents, Maria and Alejandro, are siblings. 

Luis is the son of Marco, who is also one of Maria's brothers. Therefore, Luis is another one of Maria's nephews. In relation to Roberto, Luis is also a first cousin, as their fathers, Marco and Roberto's mother, Maria, are siblings. 

Maria's relationship to Luis is that of an aunt, as she is the sister of Luis's father, Marco.
Roberto is Maria's son. Maria has two brothers, Alejandro and Marco. Alejandro has two children, Ricardo and Sofia. Marco has a son named Luis. What is the relationship between Sofia and Roberto, and between Luis and Roberto? Additionally, what is Maria's relationship to Luis?

Provide a very brief response.