It actually doesn't matter if he was a twin. The guys jeans do not determine if it will be twins or not. It is the women's. It depends on her because of her eggs. Everyone normally has only one egg. If you have one egg and it splits in two they become identical twins. If you produce two eggs you get fraternal twins. Women around their thirties or more have a higher chance in having fraternal twins because of their hormone levels causing them to produce more then one egg.