Is this normal about the Dominican culture?

This is kind of a weird question lol. My sister is engaged to a man she met in D.R.; however, he has a child (I don’t think he has custody), but he does spend time with him. He’s planning to move to the U.S. and leaving his child in D.R. I find that a huge red flag, but my mom see’s nothing wrong with this, in fact she says “that’s their culture”. I don’t know a lot about the Dominican culture, but is this something they normally do?