Yes, they didn't mention "cousin" Elizabeth and John the Baptist (I don't think). But John undoubtedly died without children, and Elizabeth being so old probably didn't have any more (I'm working from memory).
Still there might be collateral bloodline from that couple.
Apart from the fascination of it, the posters are correct that it doesn't matter because whether related by blood or not, all are saved through Christ.
Sorry, I was wrong. They did mention Elizabeth. My bad.