Leo is close to hitting the top 100 for boys in the U.S., thanks to the popularity of Leonardo DiCaprio, who usually goes by the shortened Leo. It's a Latin name with a cool meaning—lion—and it was used for literally a dozen Popes and many saints.
Lenny is usually short for Leonard—which means that he's essentially giving his two sons the same name. (Leonard also means lion.) However, Lenny hasn't fared quite as well as the cooler "Leo" nickname—it fell out of the top 1000 in the early 1980s, probably thanks to the doofus neighbors Lenny and Squiggy on the show Laverne and Shirley.
No word yet on the middle names, but I find it interesting that both sets of twins have one child with an "in vogue" name (Myla and Leo), and one with a retro choice (Charlene and Lenny).
What do you think of the names they picked? Would you go for Lenny or Leo?