That story reminded me of the promise to Abraham that God would make him a great nation (Gen 12:2) and that his offspring would be as numerous as the stars of the heaven (Gen 15:4-5). Abraham lived much longer ago than Genghis Khan, so presumably he would have more than 16 million descendants. Still, even 16 million is a large number to think about and to consider the ramifications of one person being on the earth - many more than for George Bailey in It's a Wonderful Life.
But wait, that's only half the story. Abraham has more than natural descendants; he has supernatural descendants. All those who belong to Christ are Abraham's seed, and if you are Abraham's seed then you are heirs of the promises made to Abraham (Gal 3:29). God's promise to Abraham was: "I will make you into a great nation and I will bless you; I will make your name great, and you will be a blessing. I will bless those who bless you, and whoever curses you I will curse; and all peoples on earth will be blessed through you" (Gen 12:2-3). That is the promise to which Christians are heirs. That is good news worthy of rejoicing.
Praise the Lord. Praise him, sun and moon, praise him, all you shining stars (Psalm 148).