Today, Castro's 2-year-old son, Starlin Jr., has his own glove, bat, shoes, batting gloves and uniform. But what Castro, 25, likes the most is watching his son learn the game at an early age.
"He almost has the same mobility I had, the same everything," Castro said of his son. "I asked my mom, I asked my dad how I was at that age, and they tell me I did exactly the same."
Starlin Jr. not only has the same agility at an early age, but he has the benefit of being the son of a big league ballplayer.
"It's different because now [my son] can have everything," Castro said. "He can have a bat, a glove. [When I was growing up], we didn't have anything. We were trying to figure out how life was going to be. It's really fun now, really fun to see him every day. He wakes me up every day in the morning. He'll say, 'Hey, Daddy, let's go play.' It's so much fun to see him."
Castro's father, Diogenes, was a fisherman in Monte Cristi, Dominican Republic, and would be on the water early. But when Castro returned home from school, his father was waiting to hit grounders and work on hitting. Diogenes would pitch little rocks for Castro to hit or they made balls by bundling two socks and wrapping them with tape.
"The person who taught me how to play baseball was my dad," Castro said. "I remember where I lived, there was an empty lot, and he would hit ground balls there every day -- every day. I'd go to school in the morning, and then go to the field."
His father did what he could, and he bought Castro his first glove when he was 6 years old. It was plastic.
"After that I didn't have a glove," Castro said. "Some people went on a vacation to the Dominican, an American guy, and they played with us in the league I was playing in, and he pitched that day and he gave me his glove.
"That's the glove I had when I had my tryout [with the Cubs]," he said. "I still have it."
Castro signed with the Cubs in October 2006 when he was 16 years old; he made his big league debut May 7, 2010, at the age of 20. But that first leather glove meant so much.
"My mom and dad didn't have any money to buy me a glove," Castro said. "That guy coming there to give me that glove -- I didn't sleep for three days. I was so excited. I kept touching my glove. It was a really good, professional baseball glove. It was so important."
Before Spring Training began this year, Castro took his son to Disneyland. Starlin Jr. loves Mickey Mouse. When dad signs a seven-year, $60 million contract, which Castro did in August 2012 with the Cubs, it's a little easier to spoil his son with such treats.
"I feel happy for [his son] because he has a dad like me who can take care of him," Castro said. "That's the most important thing."
Starlin Jr. does have high expectations.
"He tells me -- when he sees me on TV -- he always says, 'Daddy, hit a homer, hit a homer,'" Castro said.
Castro and his girlfriend are expecting their second child this month. He will be able to provide both children an education in the U.S. as well as Mickey Mouse toys and baseball gloves.
"It's awesome," Castro said about being a father. "Sometimes, we come here and have a bad game and we lose, and we go home tired. I see that little guy, and the tired is gone. He gives me love all the time."