The most likely explanation for Sophia and Gio greeting each other with a kiss on each cheek is cultural norms and traditions. Different cultures have different customs when it comes to greetings and displays of affection. In some cultures, such as many European countries, kissing on the cheek is a common way to greet friends and family members. It is a gesture of warmth, familiarity, and affection.
In the example you provided, Sophia and Gio's cultural background or family traditions might include the practice of greeting each other with a kiss on each cheek. This could be a way for them to show their closeness and strengthen their bond as siblings.
It's important to remember that greetings and displays of affection can vary widely across different cultures and even within families. What may seem unusual or unfamiliar to us might be perfectly normal and customary for others. Understanding and respecting these cultural differences helps promote tolerance and appreciation for diversity.