This may contain spoilers, but oh well. Yes they are gonna have kids. How? The answer will be revealed in the story. ( So READ IT!) Anyway the one John is holding is named Hamish (it's tradition by now.) and the one Sherlock is holding is named Moris.
Author's note: I just realized I love drawing a single child or twins and they're always boys...Maybe it's because someday I would like to have kids. Either one boy or twins. Just saying. Look at my pics of children and you'll see.