Roberto is married to Isabella, and they have three children: Marco, Sophia, and Lucia. Isabella has a brother named Matteo, who has two sons named Gianluca and Stefano, and a daughter named Francesca. Describe how Gianluca and Lucia might be related to Matteo and Isabella, respectively, and explain the relationship between Francesca and Roberto.

Respond very briefly.
Gianluca and Lucia are first cousins. Gianluca is the son of Matteo, who is Isabella's brother. Since Lucia is Isabella's daughter, and Gianluca is Isabella's nephew, Lucia and Gianluca share one set of grandparents on Isabella's side, making them first cousins.

Matteo is Lucia's maternal uncle since he is Isabella's brother and Isabella is Lucia's mother. That makes Matteo Lucia's uncle on her mother's side.

Francesca is Roberto's niece through marriage. Because Francesca is Matteo's daughter and Matteo is Isabella's brother, Francesca is Isabella's niece. Since Roberto is married to Isabella, Francesca is Roberto's niece by marriage, not by blood.