HOW TO deal with people who have NO patience?

HOW TO deal with people who have NO patience? Not even strangers but even with my family members, they often don't have the patience to let me finish. Not in a rude way but they just don't have patience. Not when I'm alone with one, then there is no problem. But with a conversation with a few, and I say something, most of the time I'm not heard or people will turn and listen to someone else. This is at its worse when I'm at a party of a family member. The more people there are the worse this problem gets.